[Bug] Boards involuntarily switching regions! (With repro)

In the past, I've had a problem where boards has apparently logged me off, and it's not possible for me to log back in, even though I'm getting my username, password, and CAPTCHA all right. Interestingly, if I looked in Red Tracker, I would that I could see posts from reds in EUW. Recently, I found that I was indeed actually changing regions, and that all I had to do to restore things to normal was use the region selector in the upper left. But this still raised the question of how I was switching regions.

I think I've figured that out too. If I view a thread on the EUW forums, it switches my region on Boards to EUW, where I do not have an account and therefore can't log in or post. I'm not actively seeking out EUW threads, but I sometimes follow links there as from aggregator sites like ReignOfGaming or Surrender@20. I suspect this also occurs with other regions and in the reverse direction.

Reproduction steps:

1. Be logged in to NA.
2. Follow a link (example) to the EUW forums, preferably in a new tab.
3. Refresh the tab in the NA boards.
4. Observe that you have been switched to the EUW region, and are no longer able to post (unless you also have an account there).
5. Use the region selector in the upper left corner of the Boards to restore things to normal.

This doesn't strike me as strictly wrong behavior, in that it's clearly just the boards trying to help, but it's working in such an opaque manner that it's easy to get switched to a new region by mistake and without knowing it.