It was used on Reddit, but not widely. Mostly by insufferable 'enlightened centrists' who didn't want to engage in good faith argument.

It's now a blanket term for "anyone left l politically left of me" used by insufferable liberals who don't want to admit that trying to curry votes from Republicans lost them the election.

For a time it was being used to describe actual Chinese and Soviet sympathisers, but given how quiet that particular group has been after the election, I suspect it was interchangable with state sponsored bot accounts.