Right now KYM goes through a lot of porn storms, ads posted as images marked NSFW, links to suspicious adult websites in the comment section. I think it would be really helpful if for the first X amount of time after making an account you can't post images, links in comments, or something like that. Because all these posts are from accounts less than an hour old.
My strongest, easy? suggestion as to how to prevent this even farther would be to add a random amount of time within a range before an account can post, like between 12 and 14 hours after creating the account or something so bots can't pin down the time exactly.
I don't even know if that's practical but I keep seeing posts that are ads and I thought I'd throw in my two cents as to how to make things worse for the spambots.