There was a special sig option back in the early days of DDO (first year-ish) that I can't find a way to unselect. so it shows this weird box now in the bottom right, for a character I haven't played in 5 yrs, and I can't get it to show the graphical sig.
(I could be wrong, but this doesn't seem the same as the "known issue" sig issue in the sticky thread.
There are very few of y'all left with that buggy lil thing, and I don't recall anyone saying how they got rid of theirs - if any ever tried.
What I'd do if was my sig... Self report your OP in this thread, and ask in the comment if your sig can be cleared. Worst that can happen is they ignore the report.