When a thread gets split from another (as happened with the “CI/Scilly fly-in in July” split from the “Alderney” one), IMHO the people that watch the old thread should automatically be set to watch the new thread.
It’s a good point; however one could argue that the transfer of the watch should be done according to how far the thread reached at the moment the watch was set 
and that gets quite complicated. Or one could argue that the old watch should also remain.
I can’t personally (as a mod) see which threads are watched but I know a lot of people set a watch very early on in a thread’s life, and might well have no interest in off-topic posts which get split off from it. I rarely split threads; I do it only when
There is a similar issue with merging threads. One also loses a lot of post numbers then. I now tend to do it mostly only when the new thread has gone more or less silent.
