I don't see that often at all. At times I've seen people do a little teasing ... in which case finishing with a smile is to invite a tease back. Sometimes things that are said are taken more seriously than they are intended. That's the problem in "talking" with strangers using only the written word.
I never give emoticons a thought ... before the web people generally wrote informally to people they knew, so there was enough trust to mean emoticons weren't needed. Emoticons are just something done on the web to allow strangers to communicate more effectively in writing, making up for the lack of facial expressions.
There is a view that emoticons reduce the gravitas of communication and those who use them are dismissed as lightweights. Sure, emoticons don't belong in formal business or academic writing. But to dismiss them in an informal forum is rather pompous and stodgy, don't you think?
If people want to be taken
seriously and see emoticons banned then they should be writing detailed and structured posts of at least 1,000 words, with references (using the Harvard system?).