It turns out that my friend Darren Terry discovered a workaround to this bug. This is what Darren had to say:
"Try making the text fields themselves physically taller (not the font size), the way people do when trying to get a layout built on a Mac to display right on Windows."
I did that, and it fixed the problem in FM 10.x and 11.x.
I made the text field physically taller by extending the height downwards while keeping the text aligned at the top, and that worked.
Interestingly enough, it DOESN'T work if you make the text field physically taller by extending the height upwards while keeping the text aligned at the bottom.
FileMaker Inc.: Please note that these field heights are the exact same heights that I've always used for these fonts in previous versions of FileMaker Pro, but for some reason, FM 10.x is now rendering them incorrectly.
Thank you for your posts.
What font are you using? Is it possible you have multiples of the same font installed? Does this occur with all fonts?