Yeah, he first came to my attention during the Boston bombing aftermath a few years ago.

His posts at the time didn't give me any cause for concern and he gave out some useful information, as he still does from time to time.

Mensch and he had a very public and bitter falling out last year, so the claim that ""He was all over the place, so she dropped him" is a laughable gloss on what actually happened. Mensch was claiming repeatedly in the media that she and The Jester were collaborating more closely than he was happy about and making outlandish claims he didn't feel were helpful or factual. If anybody did the "ditching", it was The Jester, and she took it very, very badly, in the way only she can.

As for "outing" his .ru email address, that "revelation" has been doing the rounds since at least 2010 (do a Google search for it if you're short of rabbit holes to fall down - many of them are circular, and the screencap in your OP doesn't have a date stamp or any other confirmatory information). Numerous attempts have been made to doxx The Jester and discredit him over the years, none successful.

The Jester's recently also fallen out with John Schindler. Schindler's set up a paid-for private Twitter space, and The Jester felt he was exploiting his position for gain. The Jester had already set up his own private, supposedly secure, online discussion venue, so I guess you could put it down to rivalry if you were so inclined. Counterchekist and Schindler seem pretty close, to add to the mix.

I know a hell of a lot less about Counterchekist and haven't paid him/she/it/them much attention, but once you take a look at some of these social media personas (Schindler included), you learn to take everything and everybody with a pinch of salt.