According to the International Phonetic Association, some glyphs of the phonetic notations of the International Phonetic Alphabet in DejaVu Sans font are not designed correctly: https://www.internationalphoneticassociation.org/content/full-ipa-chart

Quotation:

• The symbol for the labiodental flap [ⱱ, Unicode: U+2C71] is not quite right in this font (and in many fonts). We recommend using the symbol from another sans serif font, SIL’s Andika, for this symbol.
• The symbol for the alveolar tap [ɾ, Unicode: U+027E] has a serif. This makes the shape more clearly different from the trill symbol. However, if a sans serif symbol is desired, the tap symbol from SIL’s Andika font can be used.
• The symbol for the voiced palatal implosive [ʄ, Unicode: U+0284] in this font has an extra half cross-bar, above the full cross-bar. Therefore the symbol shown here is made by combining 0283+0335.
• The Laminal diacritic [Unicode: U+033B] is square and small, and therefore tends to be confused with the voiceless diacritic [U+0325]. We recommend that this diacritic be made extra-large so that its shape is clearly a square, not a circle. (In IPA Kiel, this diacritic is correctly a rectangle.)
• The exact tone contour [˥, Unicode: U+02E5] shown in the Rising-falling tone letter [˨˥˨, Unicode: 02E8 + 02E5 + 02E8] is different from IPA Kiel’s.
• The shape of the Velarized diacritic [ˠ, Unicode: U+02E0] is not quite the same as that of the voiced velar fricative [ɣ, Unicode: U+0263].
• A problem for all fonts, due to the design of symbols introduced in 1989, is that the distinctions between the dental click [ǀ, Unicode: U+01C0] and the minor group [|, Unicode: U+007C], and between the lateral click [ǁ, Unicode: U+01C1] and the major group [‖, Unicode: U+2016], are small at best. At the time of the Kiel convention, it was suggested that the grouping symbols be thicker than the click symbols. In the 2005 chart, the grouping symbols were in bold, and that is true of the 2015 charts as well. In addition, in sans serif fonts the alveolar lateral approximant is likely to be similar to both the dental click and the minor group. DejaVu does a relatively good job of keeping these distinct through line length and thickness.