It is so tricky and i dont have any good answers as I'm a tech-idiot, but I'll try my best to give you some suggestions:

In the past you may come across a comment that sounded overly robotic and emotionless when they commented, but that might as well just be someone on the spectrum. Nowadays some bot comments sound more human than actual human comments. I really cannot tell.

I think I was often accused of being a bot because I tend to go into detail about things that interest me and try to explain things in too many paragraphs, lol. I have tried to learn how to shorten my replies to people but I fucking fail everytime. I literally just spammed a friend with a long ramble about why the Syrian flag looks different and went into the history of the flag and made a cliff notes version of the conflict in Syria because it randomly became an interest for me for a few minutes after a car passed my window with the new Syrian flag on the car helmet. So maybe that trait is a bit off putting to random people who cross my path online. I dunno.

Anyway, I have heard that some people look at sentence structure and grammar to decipher who is real and who isn't. If the grammar is too good, the sentence structures too perfect, then some people suspect it is a bot. But it's probably just a matter of time before bots will adapt to poor grammar and writing patterns. If they can go from sounding like a Wikipedia page to cracking jokes and sounding human in less than five years, they can learn how to imitate shitty writing patterns that most of us have. I for one tend to accidentally press the s when I want to press the a and I usually catch it before posting, but sometimes I overlook it.

Usually, on reddit, I would check the comment history of someone I suspected of being a bot. If they posted way too much, like seconds between each comment and in various different subs for hours, I would conclude they were a bot, but I don't think all bots are like that.

I dunno how I would spot bots in the fediverse, tbh. Maybe similar, checking the comment history if i suspect a bot, but otherwise i dunno man.

Usually I go by how people behave. Anyone who acts insane or aggressive gets blocked. I am too old to deal with shit like that, but that has less to do with bots and more to do with no longer tolerating extremely divisive behavior.