There's been some updates where it was easier to move the modifications to the new files. It sounds like a lot of the updates were stripping trailing spaces, converting spaces to tabs, etc. Unless you're very familiar with your own changes, it's going to be difficult to update to this one using any simple file compare - most lines will trigger differences.
Allen, you're absolutely correct in this, and your suggested procedure of moving your site's custom modifications into the 7.5.9 release, rather than the other way around.
To help you do-it-yourselfers out, I'll have a quick BeyondCompare tutorial up in a few hours for doing just that.
In this 7.5.9 release of UBB.threads -- if coming from 7.5.8-r2 -- every directory is mostly "modular."
/languages/english files can be be installed without affecting anything.
Also, /templates/default are independent of everything.
/admin doesnt require any additional dependencies, nor do the files within /libs or /scripts.
IIRC, everything updated in 7.5.9 should be modular. That's your pro-tip for today.
The feature list for the next release of UBB.threads will most likely have changes that will be dependent upon other files. UBB.threads 7.5.9 lays down a foundation for those things.
I AM HERE TO DRINK COFFEE AND KICK ASS. AND RIGHT NOW, I AM ALL OUT OF COFFEE.
(caps. sorry. but they do add more feeling