Created attachment 123095 [details]
This is printed via PDFCreator, you can see what I have seen

Several romanizations of Chinese dialects has some diacritics with less-known usage for typographic designers.

1. Pe̍h-ōe-jī use O͘ for pronounciation [ɔ], use a short vertical line for tone 8.
2. Foochow, Hinghwa and Kienning Romanizations (Bàng-uâ-cê, Báⁿ-uā-ci̍, Gṳ̄̄ing-nǎing Lô̤-mǎ-cī) use diaeresis below to dictinct some vowels.
3. Kienning Colloquial Romanized use macron twice on a letter for tone 4.
4. Min Nan syllabic consonant m and ng written in POJ and accented æ used in Hainan Romanized (Bǽh-oe-tu)

I create the following into https://wymeditor.github.io/wymeditor/dist/examples/01-basic.html , using Firefox 45.0.2 on Windows 10

<div style="font-family: DejaVu Serif; font-size:2em; line-height:1.1em">
<p>O͘Ó͘Ò͘Ô͘Ō͘O̍͘o͘ó͘ò͘ô͘ō͘o̍͘ <i>O͘Ó͘Ò͘Ô͘Ō͘O̍͘o͘ó͘ò͘ô͘ō͘o̍͘</i> <b>O͘Ó͘Ò͘Ô͘Ō͘O̍͘o͘ó͘ò͘ô͘ō͘o̍͘ <i>O͘Ó͘Ò͘Ô͘Ō͘O̍͘o͘ó͘ò͘ô͘ō͘o̍͘</i></b></p>
<p style="font-feature-settings: 'smcp' on, 'c2sc' on">O͘Ó͘Ò͘Ô͘Ō͘O̍͘o͘ó͘ò͘ô͘ō͘o̍͘ <i>O͘Ó͘Ò͘Ô͘Ō͘O̍͘o͘ó͘ò͘ô͘ō͘o̍͘</i> <b>O͘Ó͘Ò͘Ô͘Ō͘O̍͘o͘ó͘ò͘ô͘ō͘o̍͘ <i>O͘Ó͘Ò͘Ô͘Ō͘O̍͘o͘ó͘ò͘ô͘ō͘o̍͘</i></b></p>
<p>O͘Ó͘Ò͘Ô͘Ō͘O̍͘o͘ó͘ò͘ô͘ō͘o̍͘ <i>O͘Ó͘Ò͘Ô͘Ō͘O̍͘o͘ó͘ò͘ô͘ō͘o̍͘</i> <b>O͘Ó͘Ò͘Ô͘Ō͘O̍͘o͘ó͘ò͘ô͘ō͘o̍͘ <i>O͘Ó͘Ò͘Ô͘Ō͘O̍͘o͘ó͘ò͘ô͘ō͘o̍͘</i></b></p>
<p style="font-feature-settings: 'smcp' on, 'c2sc' on">O͘Ó͘Ò͘Ô͘Ō͘O̍͘o͘ó͘ò͘ô͘ō͘o̍͘ <i>O͘Ó͘Ò͘Ô͘Ō͘O̍͘o͘ó͘ò͘ô͘ō͘o̍͘</i> <b>O͘Ó͘Ò͘Ô͘Ō͘O̍͘o͘ó͘ò͘ô͘ō͘o̍͘ <i>O͘Ó͘Ò͘Ô͘Ō͘O̍͘o͘ó͘ò͘ô͘ō͘o̍͘</i></b></p>
<p>A̍E̍I̍O̍U̍a̍e̍i̍o̍u̍ <i>A̍E̍I̍O̍U̍a̍e̍i̍o̍u̍</i> <b>A̍E̍I̍O̍U̍a̍e̍i̍o̍u̍ <i>A̍E̍I̍O̍U̍a̍e̍i̍o̍u̍</i></b></p>
<p style="font-feature-settings: 'smcp' on, 'c2sc' on">A̍E̍I̍O̍U̍a̍e̍i̍o̍u̍ <i>A̍E̍I̍O̍U̍a̍e̍i̍o̍u̍</i> <b>A̍E̍I̍O̍U̍a̍e̍i̍o̍u̍ <i>A̍E̍I̍O̍U̍a̍e̍i̍o̍u̍</i></b></p>
<p>A̤Ă̤Ā̤Á̤À̤Â̤E̤Ĕ̤Ē̤É̤È̤Ê̤O̤O̤Ŏ̤Ó̤Ò̤Ô̤ṲṲ̆Ṳ́Ṳ̀Ṳ̂a̤ă̤ā̤á̤à̤â̤e̤ĕ̤ē̤é̤è̤ê̤o̤o̤ŏ̤ó̤ò̤ô̤ṳṳ̆ṳ́ṳ̀ṳ̂ <i>A̤Ă̤Ā̤Á̤À̤Â̤E̤Ĕ̤Ē̤É̤È̤Ê̤O̤O̤Ŏ̤Ó̤Ò̤Ô̤ṲṲ̆Ṳ́Ṳ̀Ṳ̂a̤ă̤ā̤á̤à̤â̤e̤ĕ̤ē̤é̤è̤ê̤o̤o̤ŏ̤ó̤ò̤ô̤ṳṳ̆ṳ́ṳ̀ṳ̂</i> <b>A̤Ă̤Ā̤Á̤À̤Â̤E̤Ĕ̤Ē̤É̤È̤Ê̤O̤O̤Ŏ̤Ó̤Ò̤Ô̤ṲṲ̆Ṳ́Ṳ̀Ṳ̂a̤ă̤ā̤á̤à̤â̤e̤ĕ̤ē̤é̤è̤ê̤o̤o̤ŏ̤ó̤ò̤ô̤ṳṳ̆ṳ́ṳ̀ṳ̂ <i>A̤Ă̤Ā̤Á̤À̤Â̤E̤Ĕ̤Ē̤É̤È̤Ê̤O̤O̤Ŏ̤Ó̤Ò̤Ô̤ṲṲ̆Ṳ́Ṳ̀Ṳ̂a̤ă̤ā̤á̤à̤â̤e̤ĕ̤ē̤é̤è̤ê̤o̤o̤ŏ̤ó̤ò̤ô̤ṳṳ̆ṳ́ṳ̀ṳ̂</i></b></p>
<p style="font-feature-settings: 'smcp' on, 'c2sc' on">A̤Ă̤Ā̤Á̤À̤Â̤E̤Ĕ̤Ē̤É̤È̤Ê̤O̤O̤Ŏ̤Ó̤Ò̤Ô̤ṲṲ̆Ṳ́Ṳ̀Ṳ̂a̤ă̤ā̤á̤à̤â̤e̤ĕ̤ē̤é̤è̤ê̤o̤o̤ŏ̤ó̤ò̤ô̤ṳṳ̆ṳ́ṳ̀ṳ̂ <i>A̤Ă̤Ā̤Á̤À̤Â̤E̤Ĕ̤Ē̤É̤È̤Ê̤O̤O̤Ŏ̤Ó̤Ò̤Ô̤ṲṲ̆Ṳ́Ṳ̀Ṳ̂a̤ă̤ā̤á̤à̤â̤e̤ĕ̤ē̤é̤è̤ê̤o̤o̤ŏ̤ó̤ò̤ô̤ṳṳ̆ṳ́ṳ̀ṳ̂</i> <b>A̤Ă̤Ā̤Á̤À̤Â̤E̤Ĕ̤Ē̤É̤È̤Ê̤O̤O̤Ŏ̤Ó̤Ò̤Ô̤ṲṲ̆Ṳ́Ṳ̀Ṳ̂a̤ă̤ā̤á̤à̤â̤e̤ĕ̤ē̤é̤è̤ê̤o̤o̤ŏ̤ó̤ò̤ô̤ṳṳ̆ṳ́ṳ̀ṳ̂ <i>A̤Ă̤Ā̤Á̤À̤Â̤E̤Ĕ̤Ē̤É̤È̤Ê̤O̤O̤Ŏ̤Ó̤Ò̤Ô̤ṲṲ̆Ṳ́Ṳ̀Ṳ̂a̤ă̤ā̤á̤à̤â̤e̤ĕ̤ē̤é̤è̤ê̤o̤o̤ŏ̤ó̤ò̤ô̤ṳṳ̆ṳ́ṳ̀ṳ̂</i></b></p>
<p>Ā̄Ā̄Ā̤̄Ā̤̄Ē̄Ē̄Ē̤̄Ē̤̄Ī̄Ī̄Ō̄Ō̄Ō̤̄Ō̤̄Ū̄Ū̄Ṳ̄̄Ṳ̄̄ā̄ā̄ā̤̄ā̤̄ē̄ē̄ē̤̄ē̤̄ī̄ī̄ō̄ō̄ō̤̄ō̤̄ū̄ū̄ṳ̄̄ṳ̄̄ <i>Ā̄Ā̄Ā̤̄Ā̤̄Ē̄Ē̄Ē̤̄Ē̤̄Ī̄Ī̄Ō̄Ō̄Ō̤̄Ō̤̄Ū̄Ū̄Ṳ̄̄Ṳ̄̄ā̄ā̄ā̤̄ā̤̄ē̄ē̄ē̤̄ē̤̄ī̄ī̄ō̄ō̄ō̤̄ō̤̄ū̄ū̄ṳ̄̄ṳ̄̄</i> <b>Ā̄Ā̄Ā̤̄Ā̤̄Ē̄Ē̄Ē̤̄Ē̤̄Ī̄Ī̄Ō̄Ō̄Ō̤̄Ō̤̄Ū̄Ū̄Ṳ̄̄Ṳ̄̄ā̄ā̄ā̤̄ā̤̄ē̄ē̄ē̤̄ē̤̄ī̄ī̄ō̄ō̄ō̤̄ō̤̄ū̄ū̄ṳ̄̄ṳ̄̄ <i>Ā̄Ā̄Ā̤̄Ā̤̄Ē̄Ē̄Ē̤̄Ē̤̄Ī̄Ī̄Ō̄Ō̄Ō̤̄Ō̤̄Ū̄Ū̄Ṳ̄̄Ṳ̄̄ā̄ā̄ā̤̄ā̤̄ē̄ē̄ē̤̄ē̤̄ī̄ī̄ō̄ō̄ō̤̄ō̤̄ū̄ū̄ṳ̄̄ṳ̄̄</i></b></p>
<p style="font-feature-settings: 'smcp' on, 'c2sc' on">Ā̄Ā̄Ā̤̄Ā̤̄Ē̄Ē̄Ē̤̄Ē̤̄Ī̄Ī̄Ō̄Ō̄Ō̤̄Ō̤̄Ū̄Ū̄Ṳ̄̄Ṳ̄̄ā̄ā̄ā̤̄ā̤̄ē̄ē̄ē̤̄ē̤̄ī̄ī̄ō̄ō̄ō̤̄ō̤̄ū̄ū̄ṳ̄̄ṳ̄̄ <i>Ā̄Ā̄Ā̤̄Ā̤̄Ē̄Ē̄Ē̤̄Ē̤̄Ī̄Ī̄Ō̄Ō̄Ō̤̄Ō̤̄Ū̄Ū̄Ṳ̄̄Ṳ̄̄ā̄ā̄ā̤̄ā̤̄ē̄ē̄ē̤̄ē̤̄ī̄ī̄ō̄ō̄ō̤̄ō̤̄ū̄ū̄ṳ̄̄ṳ̄̄</i> <b>Ā̄Ā̄Ā̤̄Ā̤̄Ē̄Ē̄Ē̤̄Ē̤̄Ī̄Ī̄Ō̄Ō̄Ō̤̄Ō̤̄Ū̄Ū̄Ṳ̄̄Ṳ̄̄ā̄ā̄ā̤̄ā̤̄ē̄ē̄ē̤̄ē̤̄ī̄ī̄ō̄ō̄ō̤̄ō̤̄ū̄ū̄ṳ̄̄ṳ̄̄ <i>Ā̄Ā̄Ā̤̄Ā̤̄Ē̄Ē̄Ē̤̄Ē̤̄Ī̄Ī̄Ō̄Ō̄Ō̤̄Ō̤̄Ū̄Ū̄Ṳ̄̄Ṳ̄̄ā̄ā̄ā̤̄ā̤̄ē̄ē̄ē̤̄ē̤̄ī̄ī̄ō̄ō̄ō̤̄ō̤̄ū̄ū̄ṳ̄̄ṳ̄̄</i></b></p>
<p>ḾM̀M̂M̄M̍ḿm̀m̂m̄m̍ŃGǸGN̂GN̄GN̍GŃGǸGńgǹgn̂gn̄gn̍gńgǹg <i>ḾM̀M̂M̄M̍ḿm̀m̂m̄m̍ŃGǸGN̂GN̄GN̍GŃGǸGńgǹgn̂gn̄gn̍gńgǹg</i> <b>ḾM̀M̂M̄M̍ḿm̀m̂m̄m̍ŃGǸGN̂GN̄GN̍GŃGǸGńgǹgn̂gn̄gn̍gńgǹg <i>ḾM̀M̂M̄M̍ḿm̀m̂m̄m̍ŃGǸGN̂GN̄GN̍GŃGǸGńgǹgn̂gn̄gn̍gńgǹg</i></b></p>
<p style="font-feature-settings: 'smcp' on, 'c2sc' on">ḾM̀M̂M̄M̍ḿm̀m̂m̄m̍ŃGǸGN̂GN̄GN̍GŃGǸGńgǹgn̂gn̄gn̍gńgǹg <i>ḾM̀M̂M̄M̍ḿm̀m̂m̄m̍ŃGǸGN̂GN̄GN̍GŃGǸGńgǹgn̂gn̄gn̍gńgǹg</i> <b>ḾM̀M̂M̄M̍ḿm̀m̂m̄m̍ŃGǸGN̂GN̄GN̍GŃGǸGńgǹgn̂gn̄gn̍gńgǹg <i>ḾM̀M̂M̄M̍ḿm̀m̂m̄m̍ŃGǸGN̂GN̄GN̍GŃGǸGńgǹgn̂gn̄gn̍gńgǹg</i></b></p>
<p>Æ̂ǼÆ̀ǢǼǢæ̂ǽæ̀ǣǽǣ <i>Æ̂ǼÆ̀ǢǼǢæ̂ǽæ̀ǣǽǣ</i> <b>Æ̂ǼÆ̀ǢǼǢæ̂ǽæ̀ǣǽǣ <i>Æ̂ǼÆ̀ǢǼǢæ̂ǽæ̀ǣǽǣ</i></b></p>
<p style="font-feature-settings: 'smcp' on, 'c2sc' on">Æ̂ǼÆ̀ǢǼǢæ̂ǽæ̀ǣǽǣ <i>Æ̂ǼÆ̀ǢǼǢæ̂ǽæ̀ǣǽǣ</i> <b>Æ̂ǼÆ̀ǢǼǢæ̂ǽæ̀ǣǽǣ <i>Æ̂ǼÆ̀ǢǼǢæ̂ǽæ̀ǣǽǣ</i></b></p>
</div>
<div style="font-family: DejaVu Sans; font-size:2em; line-height:1.1em">
<p>O͘Ó͘Ò͘Ô͘Ō͘O̍͘o͘ó͘ò͘ô͘ō͘o̍͘ <i>O͘Ó͘Ò͘Ô͘Ō͘O̍͘o͘ó͘ò͘ô͘ō͘o̍͘</i> <b>O͘Ó͘Ò͘Ô͘Ō͘O̍͘o͘ó͘ò͘ô͘ō͘o̍͘ <i>O͘Ó͘Ò͘Ô͘Ō͘O̍͘o͘ó͘ò͘ô͘ō͘o̍͘</i></b></p>
<p style="font-feature-settings: 'smcp' on, 'c2sc' on">O͘Ó͘Ò͘Ô͘Ō͘O̍͘o͘ó͘ò͘ô͘ō͘o̍͘ <i>O͘Ó͘Ò͘Ô͘Ō͘O̍͘o͘ó͘ò͘ô͘ō͘o̍͘</i> <b>O͘Ó͘Ò͘Ô͘Ō͘O̍͘o͘ó͘ò͘ô͘ō͘o̍͘ <i>O͘Ó͘Ò͘Ô͘Ō͘O̍͘o͘ó͘ò͘ô͘ō͘o̍͘</i></b></p>
<p>O͘Ó͘Ò͘Ô͘Ō͘O̍͘o͘ó͘ò͘ô͘ō͘o̍͘ <i>O͘Ó͘Ò͘Ô͘Ō͘O̍͘o͘ó͘ò͘ô͘ō͘o̍͘</i> <b>O͘Ó͘Ò͘Ô͘Ō͘O̍͘o͘ó͘ò͘ô͘ō͘o̍͘ <i>O͘Ó͘Ò͘Ô͘Ō͘O̍͘o͘ó͘ò͘ô͘ō͘o̍͘</i></b></p>
<p style="font-feature-settings: 'smcp' on, 'c2sc' on">O͘Ó͘Ò͘Ô͘Ō͘O̍͘o͘ó͘ò͘ô͘ō͘o̍͘ <i>O͘Ó͘Ò͘Ô͘Ō͘O̍͘o͘ó͘ò͘ô͘ō͘o̍͘</i> <b>O͘Ó͘Ò͘Ô͘Ō͘O̍͘o͘ó͘ò͘ô͘ō͘o̍͘ <i>O͘Ó͘Ò͘Ô͘Ō͘O̍͘o͘ó͘ò͘ô͘ō͘o̍͘</i></b></p>
<p>A̍E̍I̍O̍U̍a̍e̍i̍o̍u̍ <i>A̍E̍I̍O̍U̍a̍e̍i̍o̍u̍</i> <b>A̍E̍I̍O̍U̍a̍e̍i̍o̍u̍ <i>A̍E̍I̍O̍U̍a̍e̍i̍o̍u̍</i></b></p>
<p style="font-feature-settings: 'smcp' on, 'c2sc' on">A̍E̍I̍O̍U̍a̍e̍i̍o̍u̍ <i>A̍E̍I̍O̍U̍a̍e̍i̍o̍u̍</i> <b>A̍E̍I̍O̍U̍a̍e̍i̍o̍u̍ <i>A̍E̍I̍O̍U̍a̍e̍i̍o̍u̍</i></b></p>
<p>A̤Ă̤Ā̤Á̤À̤Â̤E̤Ĕ̤Ē̤É̤È̤Ê̤O̤O̤Ŏ̤Ó̤Ò̤Ô̤ṲṲ̆Ṳ́Ṳ̀Ṳ̂a̤ă̤ā̤á̤à̤â̤e̤ĕ̤ē̤é̤è̤ê̤o̤o̤ŏ̤ó̤ò̤ô̤ṳṳ̆ṳ́ṳ̀ṳ̂ <i>A̤Ă̤Ā̤Á̤À̤Â̤E̤Ĕ̤Ē̤É̤È̤Ê̤O̤O̤Ŏ̤Ó̤Ò̤Ô̤ṲṲ̆Ṳ́Ṳ̀Ṳ̂a̤ă̤ā̤á̤à̤â̤e̤ĕ̤ē̤é̤è̤ê̤o̤o̤ŏ̤ó̤ò̤ô̤ṳṳ̆ṳ́ṳ̀ṳ̂</i> <b>A̤Ă̤Ā̤Á̤À̤Â̤E̤Ĕ̤Ē̤É̤È̤Ê̤O̤O̤Ŏ̤Ó̤Ò̤Ô̤ṲṲ̆Ṳ́Ṳ̀Ṳ̂a̤ă̤ā̤á̤à̤â̤e̤ĕ̤ē̤é̤è̤ê̤o̤o̤ŏ̤ó̤ò̤ô̤ṳṳ̆ṳ́ṳ̀ṳ̂ <i>A̤Ă̤Ā̤Á̤À̤Â̤E̤Ĕ̤Ē̤É̤È̤Ê̤O̤O̤Ŏ̤Ó̤Ò̤Ô̤ṲṲ̆Ṳ́Ṳ̀Ṳ̂a̤ă̤ā̤á̤à̤â̤e̤ĕ̤ē̤é̤è̤ê̤o̤o̤ŏ̤ó̤ò̤ô̤ṳṳ̆ṳ́ṳ̀ṳ̂</i></b></p>
<p style="font-feature-settings: 'smcp' on, 'c2sc' on">A̤Ă̤Ā̤Á̤À̤Â̤E̤Ĕ̤Ē̤É̤È̤Ê̤O̤O̤Ŏ̤Ó̤Ò̤Ô̤ṲṲ̆Ṳ́Ṳ̀Ṳ̂a̤ă̤ā̤á̤à̤â̤e̤ĕ̤ē̤é̤è̤ê̤o̤o̤ŏ̤ó̤ò̤ô̤ṳṳ̆ṳ́ṳ̀ṳ̂ <i>A̤Ă̤Ā̤Á̤À̤Â̤E̤Ĕ̤Ē̤É̤È̤Ê̤O̤O̤Ŏ̤Ó̤Ò̤Ô̤ṲṲ̆Ṳ́Ṳ̀Ṳ̂a̤ă̤ā̤á̤à̤â̤e̤ĕ̤ē̤é̤è̤ê̤o̤o̤ŏ̤ó̤ò̤ô̤ṳṳ̆ṳ́ṳ̀ṳ̂</i> <b>A̤Ă̤Ā̤Á̤À̤Â̤E̤Ĕ̤Ē̤É̤È̤Ê̤O̤O̤Ŏ̤Ó̤Ò̤Ô̤ṲṲ̆Ṳ́Ṳ̀Ṳ̂a̤ă̤ā̤á̤à̤â̤e̤ĕ̤ē̤é̤è̤ê̤o̤o̤ŏ̤ó̤ò̤ô̤ṳṳ̆ṳ́ṳ̀ṳ̂ <i>A̤Ă̤Ā̤Á̤À̤Â̤E̤Ĕ̤Ē̤É̤È̤Ê̤O̤O̤Ŏ̤Ó̤Ò̤Ô̤ṲṲ̆Ṳ́Ṳ̀Ṳ̂a̤ă̤ā̤á̤à̤â̤e̤ĕ̤ē̤é̤è̤ê̤o̤o̤ŏ̤ó̤ò̤ô̤ṳṳ̆ṳ́ṳ̀ṳ̂</i></b></p>
<p>Ā̄Ā̄Ā̤̄Ā̤̄Ē̄Ē̄Ē̤̄Ē̤̄Ī̄Ī̄Ō̄Ō̄Ō̤̄Ō̤̄Ū̄Ū̄Ṳ̄̄Ṳ̄̄ā̄ā̄ā̤̄ā̤̄ē̄ē̄ē̤̄ē̤̄ī̄ī̄ō̄ō̄ō̤̄ō̤̄ū̄ū̄ṳ̄̄ṳ̄̄ <i>Ā̄Ā̄Ā̤̄Ā̤̄Ē̄Ē̄Ē̤̄Ē̤̄Ī̄Ī̄Ō̄Ō̄Ō̤̄Ō̤̄Ū̄Ū̄Ṳ̄̄Ṳ̄̄ā̄ā̄ā̤̄ā̤̄ē̄ē̄ē̤̄ē̤̄ī̄ī̄ō̄ō̄ō̤̄ō̤̄ū̄ū̄ṳ̄̄ṳ̄̄</i> <b>Ā̄Ā̄Ā̤̄Ā̤̄Ē̄Ē̄Ē̤̄Ē̤̄Ī̄Ī̄Ō̄Ō̄Ō̤̄Ō̤̄Ū̄Ū̄Ṳ̄̄Ṳ̄̄ā̄ā̄ā̤̄ā̤̄ē̄ē̄ē̤̄ē̤̄ī̄ī̄ō̄ō̄ō̤̄ō̤̄ū̄ū̄ṳ̄̄ṳ̄̄ <i>Ā̄Ā̄Ā̤̄Ā̤̄Ē̄Ē̄Ē̤̄Ē̤̄Ī̄Ī̄Ō̄Ō̄Ō̤̄Ō̤̄Ū̄Ū̄Ṳ̄̄Ṳ̄̄ā̄ā̄ā̤̄ā̤̄ē̄ē̄ē̤̄ē̤̄ī̄ī̄ō̄ō̄ō̤̄ō̤̄ū̄ū̄ṳ̄̄ṳ̄̄</i></b></p>
<p style="font-feature-settings: 'smcp' on, 'c2sc' on">Ā̄Ā̄Ā̤̄Ā̤̄Ē̄Ē̄Ē̤̄Ē̤̄Ī̄Ī̄Ō̄Ō̄Ō̤̄Ō̤̄Ū̄Ū̄Ṳ̄̄Ṳ̄̄ā̄ā̄ā̤̄ā̤̄ē̄ē̄ē̤̄ē̤̄ī̄ī̄ō̄ō̄ō̤̄ō̤̄ū̄ū̄ṳ̄̄ṳ̄̄ <i>Ā̄Ā̄Ā̤̄Ā̤̄Ē̄Ē̄Ē̤̄Ē̤̄Ī̄Ī̄Ō̄Ō̄Ō̤̄Ō̤̄Ū̄Ū̄Ṳ̄̄Ṳ̄̄ā̄ā̄ā̤̄ā̤̄ē̄ē̄ē̤̄ē̤̄ī̄ī̄ō̄ō̄ō̤̄ō̤̄ū̄ū̄ṳ̄̄ṳ̄̄</i> <b>Ā̄Ā̄Ā̤̄Ā̤̄Ē̄Ē̄Ē̤̄Ē̤̄Ī̄Ī̄Ō̄Ō̄Ō̤̄Ō̤̄Ū̄Ū̄Ṳ̄̄Ṳ̄̄ā̄ā̄ā̤̄ā̤̄ē̄ē̄ē̤̄ē̤̄ī̄ī̄ō̄ō̄ō̤̄ō̤̄ū̄ū̄ṳ̄̄ṳ̄̄ <i>Ā̄Ā̄Ā̤̄Ā̤̄Ē̄Ē̄Ē̤̄Ē̤̄Ī̄Ī̄Ō̄Ō̄Ō̤̄Ō̤̄Ū̄Ū̄Ṳ̄̄Ṳ̄̄ā̄ā̄ā̤̄ā̤̄ē̄ē̄ē̤̄ē̤̄ī̄ī̄ō̄ō̄ō̤̄ō̤̄ū̄ū̄ṳ̄̄ṳ̄̄</i></b></p>
<p>ḾM̀M̂M̄M̍ḿm̀m̂m̄m̍ŃGǸGN̂GN̄GN̍GŃGǸGńgǹgn̂gn̄gn̍gńgǹg <i>ḾM̀M̂M̄M̍ḿm̀m̂m̄m̍ŃGǸGN̂GN̄GN̍GŃGǸGńgǹgn̂gn̄gn̍gńgǹg</i> <b>ḾM̀M̂M̄M̍ḿm̀m̂m̄m̍ŃGǸGN̂GN̄GN̍GŃGǸGńgǹgn̂gn̄gn̍gńgǹg <i>ḾM̀M̂M̄M̍ḿm̀m̂m̄m̍ŃGǸGN̂GN̄GN̍GŃGǸGńgǹgn̂gn̄gn̍gńgǹg</i></b></p>
<p style="font-feature-settings: 'smcp' on, 'c2sc' on">ḾM̀M̂M̄M̍ḿm̀m̂m̄m̍ŃGǸGN̂GN̄GN̍GŃGǸGńgǹgn̂gn̄gn̍gńgǹg <i>ḾM̀M̂M̄M̍ḿm̀m̂m̄m̍ŃGǸGN̂GN̄GN̍GŃGǸGńgǹgn̂gn̄gn̍gńgǹg</i> <b>ḾM̀M̂M̄M̍ḿm̀m̂m̄m̍ŃGǸGN̂GN̄GN̍GŃGǸGńgǹgn̂gn̄gn̍gńgǹg <i>ḾM̀M̂M̄M̍ḿm̀m̂m̄m̍ŃGǸGN̂GN̄GN̍GŃGǸGńgǹgn̂gn̄gn̍gńgǹg</i></b></p>
<p>Æ̂ǼÆ̀ǢǼǢæ̂ǽæ̀ǣǽǣ <i>Æ̂ǼÆ̀ǢǼǢæ̂ǽæ̀ǣǽǣ</i> <b>Æ̂ǼÆ̀ǢǼǢæ̂ǽæ̀ǣǽǣ <i>Æ̂ǼÆ̀ǢǼǢæ̂ǽæ̀ǣǽǣ</i></b></p>
<p style="font-feature-settings: 'smcp' on, 'c2sc' on">Æ̂ǼÆ̀ǢǼǢæ̂ǽæ̀ǣǽǣ <i>Æ̂ǼÆ̀ǢǼǢæ̂ǽæ̀ǣǽǣ</i> <b>Æ̂ǼÆ̀ǢǼǢæ̂ǽæ̀ǣǽǣ <i>Æ̂ǼÆ̀ǢǼǢæ̂ǽæ̀ǣǽǣ</i></b></p>
</div>

The results for me are:

1. The height of dot above right looks so tall in lowercase, this dot shouldn't be higher than macron in any lettercase.
2. Diaerasis below placed incorrect in some cases, and U with diaerasis below and other diacritic completely failed.
3. Both sans and serif were failed to implement tone 4 of Kienning Romanization
4. Æ is incrrect in DejaVu Sans.

More on these romanizations:
https://en.wikipedia.org/wiki/Pe%CC%8Dh-%C5%8De-j%C4%AB
https://en.wikipedia.org/wiki/Foochow_Romanized
https://en.wikipedia.org/wiki/Kienning_Colloquial_Romanized
https://en.wikipedia.org/wiki/Hainan_Romanized