At some rasterized pixel sizes, the phonorecord copyright symbol (U+2117) -- which is present in Sans, Sans Light, and Sans Condensed -- demonstrates hinting irregularities as compared the regular copyright symbol (U+00A9).
The regular symbol's circle is always uniform and the letter inside maintains its basic shape at all point sizes, whereas the phonorecord symbol's circle is sometimes pointed on top, and the top or bottom of the curved part of the "P" is sometimes at an angle.
The two symbols are often found in proximity to each other in text, so any differences can be noticeable. The two should match, aesthetically.
I will submit a screenshot showing the effect in GDI apps. I don't know if it's observable in FreeType.
U+2117 doesn't haven any hinting in any DejaVu fonts at the moment. Condensed fonts and ExtraLight don't have any hinting at all.
Non hinted glyphs (character shapes) will not look good with GDI or when anti-aliasing isn't used. There are many glyphs that aren't hinted and we're in the slow and tedious process of hinting them.