A little search on VIM Syntax highlighting helped me write this line of code who does almost the whole work when added to ~/.vim/after/syntax/tex.vim
(you may need to create the directory in your ~/.vim
directory):
syn region texComment start="\\begin{comment}" end="\\end{comment}"
My only problem is that it can't find how to disable the matching if it encounters end-of-file before end of comment environment. Anyone has a work-around ?
NB : This command does not support nesting, which is a good thing since Latex neither and you will most likely have unmatched \end{comment}