Font Forum

I'm planning on making my font with a stylistic set that includes lines: I have a plan on how to do this by creating characters with the lines in different widths, set Advance Width of each to zero, and then make multiple substitutions. For instance substitute "a" for the lines character + "a".
Now all I'd like to know is if it might be a problem in any program that the letters and lines overlap. I've tried it with Word and it looks fine, but I'm not sure about other programs.

Why not create a Stylistic Set of the characters with lines, and use a single substitution?

That would be a way too, sure. But then due to kerning the lines would overlap with the ones of the letters before and after. So it would still be interesting to know if that could cause problems.