Are there other sites forbidding SQL developer to use c style comments? My personal opinion is that C style comments should not be used by sql developers.

The problem with C Style comments is, that they do not nest.

C Style comments are one of the lifesavers for the support when they have to do some ad hoc corrections in stored procedures, but that only works well, when they don't have to fight with existing C comments.
I never use C-style comments in SQL code.  First off, Management Studio gives a very easy way to comment out blocks of code with SQL-style commenting, and just as easy to uncomment it out.

And not to mention if another person opens a SQL script file not in SSMS, C-style comments have a tendency to be elusive and the commented out code doesn't look so commented.

Just my opinion, but I stay away from C-style commenting.  No gain.