Go to Gmail Settings > General, choose Hebrew (עברית) as the Gmail display language and click Save Changes. Once Gmail reloads in Hebrew, it looks like "&$" (sometimes followed by stray markup) appears all over the place (seems to happen before LTR embedded text). (To return to your favorite, supported LTR language, click the third blue link from the left at the top to get to Settings, then choose the language from the pop-up, and click the left button at the bottom).
Hebrew GMail performs correctly in Macintosh Firefox. Google bug id=193318
The first problem seems to be that JavaScriptCore's String.prototype.replace doesn't support the '$&' replacement code.
The workaround for Gmail is to use $0 instead of $& in your replacement strings (Firefox doesn't recognize $0 so you'd need a different code path for WebKit).
I've entered your diagnosis and workaround on the Google internal bug database entry for Google's bug id=193318
It appears that the underlying issue was fixed and I can't reproduce this in gmail, can this bug be closed?
Hi Jeremy- It's Shoshannah :-) This bug is based on a report I passed on to mitz at the days of the inital RTL gmail release. This bug is now long gone, so from me it's ok if it's closed. Mitz- do you object?
Closing as there do not appear to be any issues besides long-fixed bug 9234.