Yeah, even if someone made a physical robot that did everything, they'd notice when it did stuff like playing for 1,000 hours without ever taking a break or talking to anyone.
Bots have long been designed to account for these types of checks by having scheduled hours and jittered breaks. Private messages and name mentions can alert the bot owner so they can respond manually. I've even seen bots that will pipe private messages to an IRC channel so that any number of restricted people can respond to the messages. It's been a long time since I've worked with game bots so I'm sure they're even more advanced now.
Yeah, I know it's always an arms race, but the trick is to always give them something they weren't anticipating that's hard to deal with in code. There are always methods that would alert a human to something odd going on that don't alert the bot's methods for perceiving its surroundings.
One of the best tricks is to show them messages via a method outside of normal chat which a normal player would see on their screen, but which a bot would not receive as 'chat'.
Just have your bot log off and "sleep" randomly for 4-10 hours every night, and log off for 15 minutes every few hours during the day. If you ever get a private message, have your system play a beep (or ping you on IRC then/Discord nowadays).
As for not talking to anyone, a surprising amount of people play MMOs just like that, so it's not really atypical for a player to never communicate. Runescape even has an account choice, "Ironman Mode", where you have to play the game self-sufficiently, and can't trade with or rely on any other players. You can still chat with other players if you want, but you don't have to.
I've seen people try that, but the admins just sit there quietly watching them loop for an hour or something, then note how long it takes them to respond to a simple hello.
Or in some games, they can send messages in a way that a human would see, but not a bot who expects the messages to come over chat. For example, waving a sign in front of the character's face with a message or whatever. It helps that the admins can also hide from normal presence detection, even though they're visible on the bot's screen, visually.
I've literally watched admins ban a bot using these precise countermeasures. The trick is to always keep giving them new things they haven't thought of to adapt to.
Some of the MMO games I've played used this gold transfer "graph" analysis that worked pretty well with really low False Positive Rate.