if I'm unable to detect the tone or intentions of a comment I'll check that user's posts to get an idea, if someone has a history of not being an asshole I'm much more likely to give them the benefit of the doubt or want to engage with them. it also helps ID spam accounts

Hey this person is talking about this subject I have just heard of. I will at some point need to go validate their information but as a shortcut I can go look at their profile and see that they are well respected in communities dedicated to that subject. Therefore I can trust their information.

Alt

This person is asking questions that sound reasonable on the surface - but when I look at their post history I see they are active in some much more extreme communities and I'm able to form the conclusion that their apparently reasonable post may not be in good faith.

As for the moderation comment, I'm trying to mitigate this slightly by having an account with the same nick on 2-3 instances and modding myself on my communities on all of them. My hope is then if one of the identities goes away, I still have access from another one.

There are accounts which farm karma artificially in order to raise the price of the account and sell it to another user. Accounts with a lot can be used for branding/free marketing, as they have legitimatcy and can gain followers through having a backlog of activity. I've also heard that people can use this legitimacy for propagandistic and misinformation reasons, although I don't think that can be confirmed.