Version: Construct2(79.4) 64bit
When you rename an object and use the delete key to remove a character you get the warning message about deleting an object. If you say no the object is renamed and you can continue as normal.
From within a project, select any object to rename.
Use a right click and select rename.
Pick any character to remove and position cursor.
Press the Delete Key on Keyboard.
The Standard Delete Object warning should now appear.
Click on no
Object has been renamed.
What I think
It would seem that although you are in the edit box, Construct2 is still checking as if you are not.
Have a good one!