I get your point as most people who do this seem to use it as a tool for trolling, though sometimes they are funny, though it is often also annoying when loads of people start to quote the changed header.
This flaw is too often abused.
I ask this seriously: is it really abused that often? Maybe I haven't noticed it because it's a problem in sections I don't visit that you do (like P&S, which I think you post in), but I haven't seen members changing the thread title all that much. Or it could be that I'm just not paying attention to it since there's really no need to.
Not often, but it is another angle people use to attack other users when they want get another dig in and it can take things off topic.
Somehow I can't see it catching on
How about also not being able to change the usernames in quotes as well?
There are two opposite sides of the allowable option to modify post title inside threads:
Advantages:- OPs or the other posters are able to modify post titles to mark changes of projects (developmental upgrades, future plans, ie.), campaigns (Open, CFNP, Full, ie.), etc.
Disadvantages:- There are many different post titles inside one thread, from OPs, or from the the other posters, that might mislead new guests.
- It will probably cause uncontrolled trollings, ie. that is what TECSHARE asked for changes.
It seems like a lot of people don't bother reading before posting. Nothing I am suggesting would prevent people from modifying subject headings anyway. All I am requesting is that replies automatically mirror the subject heading in the original post, which may then be edited if so desired.
I dunno. Is this feature even necessary? The thing you seem to be complaining about is a minor thing compared to people using it to just troll. I'm not sure whether full on making it so others can't change the topic title would be better, but when users use it troll maybe those posts can be reported to be edited if they're off topic.
It is not a flaw 
