I think you'll find it's generally Americans who use the smileys and so forth.

This side of the Atlantic, unless you say you actually mean something that could be controversial, it tends to be assumed it's meant ironically. My impression is that in America it tends to be the other way round - if there's no signal that a remark is ironically meant, it tends to be taken as meant seriously.

Hence the widespread misinterpretation, which expresses itself as "Americans don't understand irony".