With the below PHP code, user can use enter all those characters in the comments form field.

PHP Code:
if (!preg_match"/^[-a-zA-Z0-9_\,\;\:\#\!\=\*\?\+\%\.\$\%\(\)\n\r]{0,600}$/" $strComments)) 
However, I did want to give them the option of using a single quote so I added \' to the regexp and it doesn't work. That is, when user enters single quote in the comment form, it results in an error - like AS IF i had restricted them from using it.

PHP Code:
if (!preg_match"/^[-a-zA-Z0-9_\,\;\:\#\!\=\*\?\'\+\%\.\$\%\(\)\n\r]{0,600}$/" $strComments)) 

Is this default behaviour or am I missing something?