Posters in this thread should be aware that their contributions will be viewed seriously as a means to help others be competent at using interweb forums.
Don't post a smiley after comments within your own post. Let someone else tell you it's funny. If no-one does, it's either not funny or you're not well liked.
You can if you do it in an ironic manner, but are you really comfortable with using irony? Well? Most people suck badly at it, particularly Americans, but if you want to try, be my guest.
Just don't come crying to me when it goes horribly wrong.