Just as an example of how I think the mods want things to work…
A few months ago, PhantomII started a thread on the F-100*.
While I was back-checking to see if any old threads had pertinent info, I found a question from a similar thread from 2006 that was never answered. Since I had recently come across the exact info the poster was asking about, I answered him… but NOT in the old thread.
I looked up the poster in the “members” area and found he was still active (had posted recently).
Since there was a currently-running thread on the aircraft, I put my answer there in the new thread, but quoting the question from the old thread and linking to it.
If, however, there had not been a currently-running thread, I would have answered in the old thread and it would have been fine, because my thread-resurrecting post would have been pertinent & relevant to that thread, and provided new info that answered an unanswered question in that thread.
* actually, he started 2 copies of the same thread, one in Historic (which quickly died from a bad case of being ignored) then the second (more successful) one in Modern Military.