Hebrew text selection seems imprecise I am not a hebrew speaker. However, looking at selecting individual characters on that page, the selection rect commonly starts/stops in the middle of glyphs (instead of between glyphs, as I would expect). This is possibly float rounding issues? Not sure. Mitz would know. Our selection is certainly better than Firefox on windows, as FF2 seems to not even always select the vowel markers(?) below the glyphs. We seem to have the correct selection height (and maybe even width), just incorrect start/stop points for the selection rect. I have not compared selection with the Mac. It's possible this is platform-only.
It's possible this is related to bug 18523
The problem is that you should now allow selection within a "cluster" for Hebrew. I think Arabic is the same. I recall being told that users expect Arabic selection to select a glyph even if it is a ligature of more than one character since that's how it looks. I think you probably want Hebrew selection to always select the vowel markers for the character it is with. We don't want to do this for some languages (think "fi" ligatures in English) but I'm not sure how to tell these apart.
I'm no longer seeing this issue, and I've not heard any complaints from actual Hebrew speakers, so closing.