Can anybody identify the blue artifact in this screenshot?

It has appeared on two different occasions while I was typing FTM posts...never elsewhere, after I hit my space bar both times, and has disappeared as soon as I hit the next key.

Thanks.

It looks like a "highlight text" artifact, the kind one gets when holding down the (left) mouse button and dragging the cursor across the line; but because it also extends down to the next line's space (without also highlighting the additional text), that's probably too facile an explanation and certainly not one that might help solve the issue (ie, whether it's a glitch on your end or FTM's).

The first two times it happened were far between, but it happened three times while I was typing my next post...always after I hit my space bar.

It's never happened in Text Edit or Mail.

I can't get it to happen under similar conditions, so if I had to hazard a guess, it's a glitch in your software (as opposed to FTM's), although I'm hard pressed to understand how.

How about clearing your FTM cookies, as well as your cache?
No idea whether those arenas might contribute to the issue, but it couldn't hurt to give it a shot.

I clear cache regularly, and the only FTM cookies I retain are those that govern log-in.

I dunno, I do a considerable amount of typing in emails, and I've never experienced my issue while doing so...only at FTM.