The most obvious characteristic of a Smurf is its giggle, so we logically begin there. We're talking Mona Lisa here. One would never mistake such a meager smile for a smirk. Postings from these Smurfs are invariably serious, though they take undisplayed joy in humorous postings by others. No raised eyebrows appear.
Usage indicates probable closet smurf.
This unmistakable characteristic indicates an unabashed delight in the silliness of others, but may indicate non-participation. These Smurfs never post original, humorous articles on their own, but they may, rarely, followup with a smart-remark. A giggle in all respects, but very quiet. Occasionally makes light fun of self or others, particularly friendly others. Enjoys a good joke.