Created attachment 326795 [details] Minimized testcase In the URL and also in the attached minimized testcase, if you select the "British Rule of Hong Kong" title and part of the surrounding paragraphs, you'll see some tall lines, whose selection box is overwriting the surrounding lines.
Created attachment 326796 [details] Screenshot Screen shot showing what I mean; the title "British Rule of Hong Kong" is partially obscured by the line "When the British took control...". I made this selection from top to bottom, e.g. I the selection starts at "ss developed communist government" and goes downwards.
This seems to work fine in FF9.0.1. If I'm missing something, please reopen with additional details.