SIL's
Font Development Best Practices recommends consistency of ascender and descender line metrics across fonts in a (R, B, I, BI) family.
Should the same hold true for OS/2.
sCapHeight and .
sxHeight? Maybe there are apps that use these values for something significant?
Comments
Most type designers keep cap height constant across most/all family members, and tend to vary x-height. Bolder styles tend to get a larger x-height. How much larger varies quite a bit.
post.underlineThickness and its shadow OS/2.yStrikeoutSize as well as post.underlinePosition are supposed to be based on the metrics of "_". However, if the thickness of "_" changes between Regular and Bold (which sounds likely) an underscore painted by an app based on the declared post metrics will change and maybe look odd.
Should I set post.underlineThickness, post.underlinePosition, OS/2.yStrikeoutSize, and OS/2.yStrikeoutPosition the same across a font family?
And yes, typographically savvy users avoid underlining if they can. However, they may be forced to by other circumstances. And one might want one's font to still look as good as possible, even when set by less savvy users.