Is that possible that you can increase maximum allowed characters in messages ?

The maximum allowed size for a message is 20000

Is that possible that this limit can be increased ? thank you

If you want to ask a questions like that here is the board to ask it in.

http://www.gamespot.com/forums/board/314159277/site-enhancements-amp-feedback

And I don't think an increase like that will be useful unless you are posting something that requires that many characters for a message.