Intuitively I used the space at first, but then I observed many other people omitting it and asked them which usage they deem correct. Until recently the outcome of my informal survey remained largely to the disfavor of the whitespace, but now I notice an increasing number of instances of deliberate use of the separating space.
Smilies are usually separated from the text, while punctuation marks are not. Personally I'm inclined to assign "^^" to the category of smilies, hence my initial use of whitespaces, but lacking solid arguments for my position I yielded to the seeming majority who omitted them.
Now I don't know anymore what to do or believe, please help!