I've noticed that the same types of encounter (e.g. one-skull thief chase) will gradually become harder as my party becomes sturdier. Yet, they don't become easier when my party is decimated. What do encounters scale to? Is it the highest level in my party? Or the average level? Or reputation?
Will mobs scale up but not scale back down?

It has always seemed to me that the mobs scale up as the days go by. Very difficult if not impossible to come back from a wipe, especially in ironman.

I was suspecting that scaling goes by time and hoping it's a bit more complex than that. Because, in that case, I probably have no other choice but to retire after a wipe once raiders start to spawn in the thief mobs.

So, in the campaign I was just playing, I was still getting groups of 7 brigand thugs at around day 120, whereas they had been replaced with packs of thugs with poachers long before day 100 in previous campaigns. So I'm not sure that time is the only factor. I got wiped by weidergangers in a cemetary quest. I had a level 5 and a level 3 survive. I probably could have rebuilt but I'm going to start a new campaign for more experimenting. I level my party as slowly as I can and see how slowly the world scales.
It would be nice to get more insight into this. Is there a forum for discussing this game that isn't dead?

There is time and party power scaling, so at certain intervals like 40 days/100 days perks are added to NPC. Gears are not included. It's party total power rather than average level so getting a few new characters won't make it easier unless your toughest 12 bros die out.

Old one uses reputation.