Can that be stopped?
You can completely disable [img] tag in bb_codes.php.
Alternatively, you can transform all [img]'s to the same format which is provided by [imgs].
are pasting their own code using [img, rather than [imgs...
Pity :) you should have your own rules for the website, and not allow others rules. Any website has its own rules.
Any user considering these rules wrong, should leave the website. Not sure what else can be done in this case.
I'm meeting this quite often. "Hey, why this and that doesn't work here
, but it works there
The answer is simple: "That's why".