My guess would be that there is an arabic letter at the end which tells the software to write/read from right to left instead of the 'western' way from left to right.
Then, when the software parses and displays that topic, everything added to the end (the pages of the thread) will be written from right to left, resulting in exactly this.
That's obviously just a guess from me, but that bugs occurs quite often in different places where the input isn't sanitized well enough.
Edit: The question mark definitely is the arabic version of the question mark. So the above written would definitely make sense here.
Edit2: It definitely is the question mark. I just created a new thread (title: "test؟") with the arabic question mark at the end and filled it with junk to reach 2 pages. It exactly behaves like the thread shown in the OP: