If you want to avoid development overhead, absolutely, C is a terrible language to pick.

I'm not sure what you mean by compatibility issues in this context?

I'm thinking about differen string representations used by different libraries. Is this not true?

Honestly all I've encountered default strings (and people shy away from those now) and LibICU stuff. I think ICU has become a defacto standard but I have been out of C for a few years.

This tends to be important for strings you're going to show to the user (or input you gather from them), maybe most of the C in the world isn't aimed at interfaces like that...