in my opinion the only REAL solution is for buyers to post VERY clear criteria and for sellers to actually READ and respect the criteria and budget posted. Aside from that, regardless of whether a member can only post/pm after x amount of time or feedback or likes or whatever the issue will remain that buyers will submit domains, be it via pm or post, that do not fit the criteria or budget and SHOULD be reported... The difference was that before it would only be the OP that would see the spam/trash and (hopefully) report it, and it could then be dealt with accordingly (pm with reminder and link to rules, friendly warning or infraction for repeat offenders) but now it 1) bumps up the thread 2) potentially prompts other "inattentive" sellers that pay more attention to the last post than to the actual criteria and budget posted by the buyer to submit MORE domains that don't fit the criteria 3) will be probably reported by several people instead of just the buyer. Also, now a buyer had to check in on their thread as well as their inbox to ensure they do not miss out on any submitted domains...
Regarding threads closing if inactive for a certain period of time I assumed that was already the case forum wide and, if not, even if implemented now the reality is the point would be defeated by (perhaps abandoned) threads being bumped up by sellers, rather than active and proactive buyers bumping their own threads to update their criteria or change in budget or to clearly signal that they are indeed still interested in domain submissions, which was a large part of why we changed it to pm only a few Years ago.