Saving photos is a good start. But In the OP's case it was contributed text that he feared lost (and is still at risk presumably):

InOBU wrote: ...all the comments of her friends many of whom are now dead... and now they are totally gone...

You'd have to be very disciplined to copy that out as a thread continues.

What's needed is a facility to archive a thread, or particular posts, when you realise that you want to keep them as in the OP's case, or it's become a valuable source.

Imagine: somebody posts a photo of a scene in a folk club and that is followed by a stream if posts identifying, and reminiscing about, the people in it.