As I could see that the code of an object (article, talk,
category ...) maight be altered / changed "automaticaly" during
save. (I assume it is the parser module making a syntax
It maight be, that the insertion of code (</nowiki> ...) would
not be, what was intended by the user.
No message is displayed and it is just another "have to know". In
similar situations I would expect a warning (as done at a
[[:en:Wikipedia:Edit conflicts]] / [[m:Help:Edit conflict]]).