Sorry, I misread.
The annoying aspect to me isn't the change in dimensions, but the inaccurate baselines. If we could reliably align text based on its baseline it wouldn't be an issue. "align-items: baseline" would be brilliant if it actually worked cross-browser.
It's pretty telling that Github doesn't even bother to solve the issue in their redesign, they've seemed to write off Firefox text alignment idiosyncrasies.