Previously, this bug was only reproduceable when the user choose to try the Acai beta. More precisely, it was linked to the new toolbar (disabling it in the preferences "fixed" the bug).

A quick fix would be to avoid sending the UsabilityInitiative related files to the users who didn't choose to try the beta (as it was the case in the beginning).

(In reply to comment #1)

Previously, this bug was only reproduceable when the user choose to try the
Acai beta. More precisely, it was linked to the new toolbar (disabling it in
the preferences "fixed" the bug).

A quick fix would be to avoid sending the UsabilityInitiative related files to
the users who didn't choose to try the beta (as it was the case in the
beginning).

This regression seems to be caused by the ClickTracking extension, I'll look at it later today.

(In reply to comment #2)

This regression seems to be caused by the ClickTracking extension, I'll look at
it later today.

Fixed this particular regression in r57978 (not live yet).

This has clearly been resolved, and is actually no longer relevant given we don't use a textarea at all anymore.

I can still reproduce (by enabling the "enhanced editing toolbar" in the Editing preferences), so I guess it isn't live yet?

(In reply to comment #4)

This has clearly been resolved, and is actually no longer relevant given we
don't use a textarea at all anymore.

That actually doesn't make it irrelevant, because browser support for Ctrl+Z in iframes isn't perfect either. The only thing that really resolves this is the side-by-side preview feature because it allows you to stay on the same page while previewing. Leaving as FIXED because we do have a solution for this in trunk (side-by-side preview).

(In reply to comment #5)

I can still reproduce (by enabling the "enhanced editing toolbar" in the
Editing preferences), so I guess it isn't live yet?

No, not yet.

Reopening as obviously it isn't fixed, though the changes are live.

*** Bug 24508 has been marked as a duplicate of this bug. ***

Seems ok Now.