When you have a constraint violation on a property value (not on one of the qualifiers), it's possible for it to overflow into the "mark as prominent" text.

Noticed this while working on T404158: "Remove" icon can run-off off the end of structured data widget items, but this is distinct enough that I figured I would make a separate ticket for it. I think it can be fixed by making the icon relatively positioned instead of absolutely positioned, though I haven't checked to see if that causes any new issues yet.