This happens (still is) a lot with me in my local section. We actually don't have our own local board yet, so we just use a megathread with 500+pages for local discussion. And the thing is, the original title is long gone, forgotten, buried. People would just make a post with their own titles, and many times we would (intentionally or unintentionally) reply or make separate comments without even changing the title, going off topic etc. It makes the thread a complete mess imo.
Having ability to change the topic title is cool, as it can be changed in the OP and in any post after that, for updating information about what's happened lately in the thread, in the company, in the discussion. You and your locals can do that in your local thread too, why not?
You can see that companies with announcement threads in forum actually change the topic title of their OP and in posts after that too. So why your local community can not do the same, no restrictions by forum rules and no reasons why your community should ignore this cool feature that can be used by topic author and by any poster in that topic. If topic authors don't want that, they can create self-moderated threads for avoiding topic title changes from community.
So, what's your personal opinion on this? Should changing/editing the title be allowed or not?
It is allowed as it has been like this for many years.
Should be allowed or not, I can answer you it should be as it should not be allowed, we don't have it now.