Basically, what I said before as quoted before. And, thanks, Thudlow, I have added the term “zombie thread” as you suggested.
Hazle, in the list of sins and malfeasances, reviving an old thread (“zombie-ism”) isn’t high on the list. In some situations, as you suggest, it’s perfectly fine. It’s almost NEVER OK in the BBQ Pit, for instance, since it’s usually just picking at old scabs.