Keg.
A thread can "drift" around a topic and still qualify as professional and relevant debate. Posts which drift a thread off to unrelated ground, are obviously fallacious, intend to mislead, are a personal attack, are agro, or are totally irrelevant are often removed.
It has always thus been since Danny wore short pants.
You've been around PPRuNe almost as long as me - I see you are entitled to your ten year certificate on April 28 this year - with 2,680 posts and I am sure you are aware of the posts to which I refer.
We very rarely if ever have problems with posts by long term PPRuNe users. New thread, first post by a new users gets a fair "scrute", particularly if an IP search indicates that user has a plethora of other user names.
It also seems to take genuine new users, time, and a number of posts before they fully understand the ethos of PPRuNe Forums.
Yes greybeard, PPRuNe is not and never has been a "free for all"! It is a private forum in the public domain, for which the forum owners (and thus the legal "publishers") are legally liable for each and every post - as we've discovered a number of times over the years!