All your base are belong to us. A modification of that is actually my signature on WhatsApp.
AmigoJack, you said it is always a bot, never a human. Did you mean in the context of what OP has described?
Human spammers are pretty much impossible to avoid. Luckily, us being a Finnish site, this is not a daily, weekly or even monthly occurence, but their latest tactic seems to be quoting a post and then changing something in that quote to insert their link or links. I find that outrageous. It is one thing to post a spam message, but modifying someone's message while quoting them is a whole new level of scum.
Surely, those could still be bots. But in one instance, I wrote something positive about a certain spammer and his post, and he then replied by liking my post. That has to be human. Are they paid by traffic of just the number of links or something else? That cannot be a very lucrative job.