Report a bug of removing a font.

I note that the following line has some problems.

\emph{\textup{(} blabla \textup{)}}

1. If I use C-c C-f C-d to remove the first "\textup" [I put the cursor 
after or before "(", but inside the {}], it will give me \emph{(} blabla 
\textup{)}, in fact I need \emph{( blabla \textup{)}}.

2. If I use C-c C-f C-d to remove the "\emph" [ I put the cursor after or 
before "blabla"], it will give me the same result as \emph{(} blabla 
\textup{)}, if fact I need
\textup{(} blabla \textup{)}.

3. It I use C-c C-f C-d to remove the second "\textup"
    a.  [If put the cursor before ")"],  it will give me \emph{\textup{(} 
after  }}, this is an error because two "}"s, in fact I need 
\emph{\textup{(} blabla )}
    b. [If put the cursor after ")"],  it will give \emph{(}  after 
\textup{)} again. In fact, I need  \emph{\textup{(} blabla )}.

4. Only when I put the cursor between "}}", it will successfully remove 
\emph.

5. The matching of brackets shows that "(}" are a pair and "{)" are another 
pair, maybe this causes the trouble.


BTW: I'm using AUCTeX 11.55
                         MikTeX 2.4
                         CVS Emacs 21.3.50.1
                         Windows XP.
--------
Best Regards,
Adam