It happens with both but it's far more noticeable in vertical mode.

I use Firefox.

Do you mean that it happens when you are in vertical mode or in horizontal mode?
Which web browser do you use?

I've noticed a strange bug on mobile. For some reason, i can no longer click on anything on the right half of the page unless i flip my phone sideways. This only happens on this website specifically.

Right, I didn't think about the 'copy image link' when clicking on the image, I just used to copy the link at the top of the page.
Solved

By the way, earlier today I fixed a small bug: the edited comments were always included in the "Last edit: ..." mention the username, but the username is supposed to appear there only when edited by someone else (an admin).

How were you doing before? Did you do a simply click and after copy the address go back to the page?
Otherwise you can still right click on the thumbnail and chose "copy link" (or "copy target" or something like that, depending on the browsers), as before. Even with the added javascript popup the link at HTML level as not changed.
Or just right click on the enlarged image displayed in the popup and chose "copy image link".
I could easily add a "copy link" button in the popup, if it is handy.

When I need to copy the link of the thumbnail, I would right click to tab the page of the browser in order to access the address bar.

The downside of the popup comment pictures is that it happens quite often to add a new page using one of those pictures: to do so I always have to click and open it in a new browser page now as I need to copy its link. Not so handy anymore if you ask me.

- Lists in admin tools are fixed
- Fixed a bug with the back/close buttons of the picture popup in "All comments" view
- In picture upload, focus is now on the first control ("Browse") rather than the first text field (URL).

It's a bug, I'll check this, thanks



No, it was killed by Facebook. Maybe it is possible to replace this by a new version (if one exists) but I'm not sure spending time on that is really worth it, since anyway it is being blocked in more and more countries for privacy reasons.