Right now they have 897 posts and 2.99K comments, so that seems a bit less than your numbers. Looking at their history they seem to be human, not a bot, and they submit news stories in bursts, which isn't as odd as if there were a constant stream of submissions. In between, they comment and discuss. I make it about 2.7 submissions or comments per hour. If they just have times each day when they binge Lemmy, that's not in itself suspicious.
For some reason, almost all of their activity is during non-working hours in a US time zone. They have bursts of activity in the morning, during a short window in the middle of the day that could be a lunch break, in the evening, and around the clock on weekends. We're currently in their morning burst, and then there will be a lull, and then there will be another short intense burst around lunchtime.
It's very unusual. What I mean by that is that posting only outside work hours is pretty normal, but the absolute firehose of activity every day during any non-work hours including lunch is abnormal. From outward appearances, it looks like a person who has a full-time job but devotes almost all of their waking hours outside that job to shitposting at full speed on Lemmy about Jill Stein.
We didn’t USED to need a rule about how many posts one could make in a day, then someone posted NINETEEN articles in a single day. Not comments, FULL ARTICLES. If you’re posting more than say, 10 or so, consider going outside and touching grass. We reserve the right to limit over-posting so a single user does not dominate the front page.