HowTO : merge the posts from 2 forums

Uhm... I wrote a long piece and now I'm not sure I get what you mean. Do you want to merge two forums on the same PunBB or to merge two different PunBBs on, say, different sites, with different users and topics, on the same PunBB?

Wow. Terrific :). Mmm, there's no automatic way to do it, but it's feasible, in a certain way. SQLing, of course :/. It depends on what you exactly want to do. You should move all the users and all the topics/posts changing all the id's correspondingly not to lose the links between them. I'd do it under extreme necessity and with lots of care, it's very, very fragile and not trivial, not at all.

I think you should better consider alternatives.

has anyone given this subject more thought, or practiced it?  it's not something i'm needing anytime soon... but it's definitely something to consider in the future: the intertwining of more than one punbb forum (separate installs).

this would be very very hard to do i think, since all the user ids and post ids would have to be worked out and also you have the problem of conflicts etc

probably but what about the user ids on the post? unless i suppose you could make one forum guest posts and the other keep the users

i dunno you could try it