The Internet is built on a lot of great people doing things for free. That doesn't have to be a bad thing if you are okay with it. But always make sure you feel good about what you are doing. If you get enjoyment or a sense of accomplishment (to quote EA) out of it then it's no worse than playing a video game or watching a tv show.
Just think about what it means to be top mod of a cities subreddit. You can trivially just delete conversations you don’t like.
Moderators have powers, use power and are often not at liberty to reveal all what went into their decisions. Moderation on any scale is however a team effort and is then subject to scrutiny, discussion and review. Power tripping moderators will be removed by the team and in communities with a sole moderator who is on a power trip it will not thrive.
Where is this mysterious subreddit, where such incredible, almost magical, things happen? Are we really talking about reddit here?
However it makes you an especially visible member of that community, especially to its worst elements. The constant hostility and eventually the harrassment made me step down.
Now I watch other moderators go through the same motions. People are absolutely vile to them, all over a tiny internet forum.
The problem with mods is that some of them behave badly enough and go on power trips banning people for their own enjoyment and making tantrums, thus giving a bad rep to the whole category, including those who are actually good people with sane principles.
Larger boards are like organization with promotions. Abuse of power won‘t earn you one. There are steering structures. Sometime one has to adjust what moderators do and have a discussion on what happened. Occasionally one has to kick a moderator out.
If you don‘t know why people help strangers then this may be worth a thing to investigate for you.