#Mod Hat Off

I agree with your line noise check criteria.

Questions about the scope of the site, INCLUDING ANY QUESTION ABOUT HURT PWECIOUS FEEWINGS OF PEOPLE WHO HAVE NOT BOTHERED TO FAMILIARIZE THEMSELVES WITH THE SITE'S SCOPE AND STATED PURPOSE are a waste of time and energy.

Server Fault's culture is very much the Usenet culture before the Eternal September - People are expected to at least have read the /about page before throwing questions on the wall. If they fail to do so swift correction is applied.
I see no issue with this so long as we're really sticking to our scope and standards and not constantly creeping the line up just to be mean.

Unless something constructive is being brought to the table -- Reconsidering the site's definition of "professional capacity", broadly including or excluding specific question categories, etc. I see no value in rehashing the same discussions.

Mod Hat On

Any discussion about the site - even the ones we've had 100000 times before - is "On Topic" for Meta by default.

My personal stance as a mod is that Meta moderation is to be undertaken with a lighter hand than even main site moderation (and I'm pretty charitable there too) -- This is the place for the minority to air their concerns. The community may not agree with the concerns raised, but it is important for the health of the site and the community that we hear them. (Also occasionally the rare valid point is brought up in those discussions -- that's how the Professionalism bit became a link in /about and /help)

That said, close voting and flagging work the same on Meta as they do anywhere else.
If something has really been covered before, it should be marked as a duplicate unless it is raising new issues/concerns not previously addressed.

Also if you guys see a discussion descending into chaos the tools to deal with that (in order of preferred application), are:

• Stating your disagreement, and ending the discussion from your end.
• Voting to close the discussion (preferably as a duplicate of something that covers the same ground, but as plain off-topic if nothing else fits).
• Flagging real trainwrecks for the mods to deal with, which may include:
  • Closure
  • Comment Purges
  • Locks
  • Deletion
  • Any combination of the above

And of course Downvotes on Meta are also the standard way of saying "I think you're wrong" / "I don't agree with this".