General rule is to NOT delete (edit down to nothing) as it destroys the context of the posts that follow.
BTW you can ask a Forum level Mod or a Greenie to correct a Subject Line or even (suggest a move if you are not the originator) MOVE the thread to a different forum.
Thread splatter is frowned upon.
necro posting is also not received well
(the forum usually pops a warning) It is better to Start a new thread if you see that.
BTW in the software forums (like Calibre, Sigil) 1 year is a really old topic even if it does not trip the warning. Those apps change rapidly