It's sad, but I can understand it. One guy with hundreds of people wanting to talk to him specifically about various aspects can get pretty overwhelming pretty quickly.
It didn't sound like it was the talking in general that was the problem... I mean, he gets that at BGG already. It sounds like it was some of the ... debating ... that was frustrating. I think.
So, my curiosity got the better of me and I went looking. It appears that these two threads were the last straw:
So when will Isotropic return? -- in which a silly question suddenly includes someone (in his first post) suggesting doing something illegal (and getting banned), Donald suggesting theory take the forums down to let people cool off, and a heated transaction between Donald and another user causes theory to lock the thread.
Goko UI makes me want to... -- in which a reasonable discussion gets derailed by the "I already paid for Dominion argument," and Donald and I end up on the same side of a heated argument with the same user as in the other thread, with a few other people on both sides. I got fed up with the thread before Donald did.
So yeah, there was your breaking point.