The debian backports 4.8 standard kernel loads the module
fjes on my thinkpad T460s.
How can I find out why this module is loaded, i.e. which hardware triggers loading this module?
You can use lspci -v. You will need to grep (probably with -i to ignore case) for your module shown in lsmod. e.g. to find r8169:
lspci -v |grep -i -A 4 -B 4 r8169
You can change the number of lines before and after (A, B) to your liking/needs.
I found another user had the same question. There is a script here to find out.