Weird thread behaviour re profile pix

Over in MSPIMS, there’s a thread about profile pix, currently over 30 posts long: So who has a profile picture?

So I started skimming it, and clicking on the occasional user’s profile to see what their picture was.

Then when I hit the “back” arrow on my browser, it takes me to a version of the thread that’s only nine posts long, ending with Kolga’s post.

What’s up with that?