Found this post while fighting ACad with this exact same problem. At least from what I managed to duplicate, it had something to do with the mtext itself. I could not replicate it with single line text, and it was not happening on other files. It only happened on one file. It happened for days (turn off computer every night), so it was a recurring problem. Everything was the same between the multiple files, that I could see anyways. This morning I decided to ctrl-c, ctrl-v some text from a good file into the bad one, and low-and-behold, the problem disappeared. I un-did that paste and the problem was still gone. I didn't save the bad file, rebooted my computer to see if I could replicate it, and no, it's gone. I have zero idea what it was, but I have always had "Intersection" turned on and only one file had this problem. I checked column settings, paragraph settings, file settings, ACad settings, everything I could think of and everything was the same between the multiple different files I checked. All I can surmise is that there is either a setting that I don't know about that allows snapping to the column/row corners (the Intersection snap points changed with the text box size adjustments, but only show up when hovering over the text itself, not the box) or it was a really odd glitch. And this is NOT related to the Node snap. That was off the entire time, and when I turned it on to test, it snapped to the same place but the hover text said Node. When I turned it off, it said Intersection again. Also, this is NOT related to the text frame. I turned that on and the snaps were not anywhere near the corners of that frame box.
Hopefully this gives some more insight for anyone having this problem.
*** EDIT: I should've known with Adsk... Well, I did nothing different, and it's back, within an hour. I had rebooted and verified and opened/closed ACad multiple times to trial/verify that it was gone and it was.... until 2min ago. Same as before, shows "Intersection" when hovering, and only on this file. I went to create a new pline and noticed it snap funny and sure enough, the mtext column corner snap is back.... Screenshot attached. Snap locations marked with lines.
More info: I attached more images. This is getting weirder as I dig into it (it's really ****ing me off). So it seems like whatever is causing this snap thing is stemming from thinking the text is lines vs other shapes? It won't show the snap when I hover near/over any (snap aperture box on) lines (hori or vert), but will if I hover over a corner or any kind of radius. See images below. Image with green: it really seems like it has something to do with ACad looking at the text as lines, and the intersections of the lines is where it pulls the Intersection snap, but since that's not a thing, it pulls the nearest snap location, being the column nodes. I can't see why it would act like that with the dot of the "i", but that's how it's acting for me.




