Generally speaking be it on IRC or forums, the unspoken rule is that if you ask for the position, you're not going to get it
I said "we need more moderators!!!!1111", they decided to promote me to mod instead. At that time, I was ambivalent about it, not knowing the cost and benefit.
Sounds similar to how I became an op on IRC... constantly bugging the opers and telling them to take care of this or that issue, making suggestions how they could do things better/faster... until one of the server admins had enough and went "There! YOU go settle it yourself"
After a few years of being oper/mod/admin in various communities, I'd only do it if I'm paid for
So those who are thinking of being one, think carefully if you do get offered, only accept an offer if you really have the spare time/energy for it. If you're thinking of wanting to be a mod just so you can shut people up or close threads you dislike, probably not a good idea to become one