Strange.
(When I click on the link I posted, it opens in a new tab. Obviously I am not talking about clicking "back" at that point because there is nothing to go back to, as you say. I mean go to the page I linked to, then click on a thread, then click "back". For instance, when I click the thread titled しないか / 水をバケツに一ぱい / とする / で(は)なければ, it seems to then take three clicks to go back.)