It's hard to convey tone of voice in text, but you can do it with capitalization and punctuation if you try.  E.g.:

No, this is the PERFECT SOLUTION! REALLY!!!! Think about it! Processing the shale in Australia is GOOD FOR THE ENVIRONMENT!!!!!

Nobody's going to take that seriously.

Whether it be sarcasm, irony or joke (humour), surely we need only the application of intelligence, not CAPITALS, or emoticons, to work out what is going on? I am reluctant to use stereotypes, but it does seem that that the non-US (I exclude Canadians)respondents on TOD seem to be much more alert to the linguistic nuances in postings on this site.

Imagine how the text of Shakespeare would look if it were deemed necessary to signal irony with capitals or italics!
Other observers have noticed a tendency towards literalism (not to mention its kin, fundamentalism) in American readers, so if this is a congenital defect that contemporay American individuals cannot be held responsible for I apologise.