I wouldn't be 100% sure about this sort of thing. For example, on this page YOU answered "You're welcome :)" to every post, but you're not a bot. When I was first here, before I knew a lot about how things worked, I posted the same message, or one of a few variants, on every giveaway I entered. It seemed rude to me NOT to post something when I was entering to win a game. I posted the messages manually. Later, when I started giving away much more stuff, I realized how silly it looks from the other side.

Repeating posts are one potential sign of bot use, yes. On the flip side, the user hasn't entered a ridiculous number of giveaways, and hasn't won large numbers of crapola games, which are also suggestive signs of bot accounts.