latex mode --- fill paragraph broken?

[iaw4]

dear emacs experts---I use binary ports for emacs under OSX, both
emacs 22 and emacs 23.  needless to say, this makes it a little bit
more complex to figure out how to get auctex to work in the newer
version.  (the older version has it built in [zenitani's emacs], but
it is no longer updated.)

so I tried out the native latex mode of emacs 23.  to my surprised,
when I tried c-q, it filled

   \x{my macro defined this}%%%
   hello

into

   \x{my macro defined this}%%% hello

this is less than desirable, of course.  is there a way to change this
behavior?

[also, as of 2011, computers have more than enough space for auctex.
is there a reason why it has not been merged into standard emacs at
this point?  is it really worthwhile to have one native mode and one
extremely-common mode for doing the same thing, and then have users
try to combine them?  of course, I have an unusual set up, so it is
more painful for me, but why not have it all in one, anyway?]

advice appreciated.

/iaw