It's pretty obvious when you look at the posts, when the thread has taken a turn "off the tracks" somewhere.
To me (and many others) it's often very useful when a thread takes a direction off the main subject into something related - and 99% of the time it IS related, sometimes funny, sometimes useful.
But very occasionally, you don't consider the direction funny or useful. You consider it obnoxious or you don't agree with the sentiment therein expressed. That happens OFTEN with me on this list. We'll be talking about an old bike, and suddenly the talk is about DLVA or SORNs or Carole Nash, EVEN IF the thread was about Ariel valve clearances originally.
That's NO problem to me at all. I don't know or care to know anything about British local bureaucracy, insurance, tax, councils, or other such issues.
So what do I do? Do I read it, and keep reading it, and then take the time and trouble to POST about it, moaning about why can't we stay on subject and why are we wasting time on this, when suddenly I'M the one extending the thread and wasting time?
That I do not. I simply quit reading the thread, and quit reading the posts on the "sequence" where it went off the rails. That way I'm not wasting my time, the people who want to discuss the pothole count in Selling village and it's so bad, isn't it? and who WANT to talk about it, can talk about it with no finger wagging and old-school-marming from me.
What's so hard about that? Why do people have to be in control of every aspect of every thread? When you start a thread, it doesn't "belong" to you any more; it belongs to anyone posting on it.
As far as Britbike goes, it's a good site, and with 20,000+ posts on it I obviously continue to think so, but many of us have found that "Political Shyte" is any thought or opinion that the moderator doesn't personally agree with, and "Non Political Posts" are any posts that the moderator DOES personally agree with; so that's sort of a bad example.
"Fighting chance of avoiding them?" It only takes a second or two to realize "Oops, there's more of that liberal/conservative/right/left crap, I'm off". However, if the problem is that the offending text is nearby somewhere, and you want it GONE even if you don't look at it, then, well ....