TITLE: Folding by Automorphisms
QUESTION [16 upvotes]: Background reading: John Stembridge's webpage.
The idea is that when you want to prove a theorem for all root systems, sometimes it suffices to prove the result for the simply laced case, and then use the concept of folding by a diagram automorphism to deduce the general case.
I have never seen an example of this in practice. So my question is: What are some (good) examples illustrating this technique?

REPLY [2 votes]: This is by now an old question, but a more recent example is given in a preprint by a current MIT graduate student
here.    I think the moral of the story is that there are quite a few directions in Lie theory where folding plays a significant role in getting from the simply-laced case to other cases.