Looks like redditors have discovered that /r/AskSocialists was taken over by the ACP. But then posts criticizing them have been getting deleted in /r/socialism, too, so seems they're also in there. Since /r/thedeprogram was shut down it doesn't seem good for the left on reddit, although at least a bunch of people are aware of the issue now.
Cpusa was infiltrated by the feds heavily back in the day, have a reputation of tailing dems in elections, but also have a deep and archived history of the american socialist movement and contain many very good people and organizers. Like most american left groups that aren't ACP or some weird Maoist cult, there are upsides and downsides.