Impersonation - Not sure this matters unless you're a mod or admin. Spamming - Just make the accounts yourself.... it's going to be infinitely easier to just make spam accounts from nothing (since it's free anyway) than to designate resources to cracking a password. Deletion/Modification of history - modlogs allow reverting ALL changes outside of full account deletion. Full account deletion - Well that's annoying at the very least. But not like it's the end of the world or has any actual cost associated with it.

It's a lot of work to do so little actual damage. It's not like twitter where hacking Elon's account can actually lead to monetary gain.