When looking at a a thread, there are links on the top and bottom right side to the previous thread/next thread.
The problem is, that the are defined in a confusing way, and assume that we look at the threads in a certain historical order, starting with the one on top. The classic definition of "previous/next" is different, so we get mixed signals.
The "previous" thread is actually the newer one and the "next thread" is the older one.
I would recommend to rename these links as "older thread/ newer thread", for example. Or something similar. 😄