OP, mate, there's definitely A LOT less spam right now than how it was back in the day when there was no merit system. I'd say Bitcointalk is in a really really great situation right now as conversations have been a lot better(at least in my opinion). Spam posts have been a lot easier to differentiate from actual constructive posts due to the lesser spam posts because of the merit system.
Much less spam as contributions of the merit system and the community to clean the forum up. People above pointed out how to use the button "Report to moderator", but I would prefer to add some more things.
[Guide] Reporting effectivelyUserscripts:
[Userscript] Report to moderator on post history[Userscript] Bitcointalk Post FilterIf you find dozens or hundreds of spam accounts in same topics, you can report them here, rather than using report to moderator.
[CLUB] The SpamBusters! Busting rule-breakers for more than a year.