I've said this elsewhere, and just to be clear I don't have any sort of contacts at Amazon or anything it's just my personal observations and I'm not taking sides/judging/whatever, but I think these emails are a lot more high level than just any X/Y batch. MTurk has everyone's entire work history from day one, it's not like they cannot look into things with some fairly simple queries and pull accounts with X # blocks / % above avg submission on Z batch / etc to start identifying accounts that might be sources of data quality that might be undesirable to requesters. People have a really hard time disassociating their work effort with their work
product and we all know on MTurk we don't really get paid for effort.
From what little we get to see they've divulged reaching out for datasets specifically looking for low quality work & the VPN'd up accounts. This one was posted this week:
So even being cheeky and thinking putting "VERY NICE" into the comment box on a survey is funny (something I've seen more than a few workers mention doing) might come back to bite you 6 months later. Could be anything similar from work history. There is a requester resource that specifically looks for some stupid things & associates a quality scored based on it & no one will know if/when the dataset is shared w/ MTurk and/or how they process it (if at all).
Maybe some emails are errors, maybe not, but it's a good opportunity to remember that a lot of things that are just a byproduct of being a human worker can be really damning when tossed into an algorithm that sorts us all based on input we don't get a say in.