Like it or not, the following are true:
we are not only rational, but also emotional human beings (not understanding this was the single biggest mistake of all European classical philosophy);
as such, we have a natural and healthy tendency to infuse all of our interactions with emotions (remember the 1997 BBC documentary about Wiles' proof of Fermat's conjecture, when Wiles begins to cry in front of the camera);
we spend more and more time communicating online, so it is natural for our natural need for emotions to invade the cold and impersonal environment of the online world;
since this is a natural, healthy manifestation of our psyche, we shouldn't fight it too much, but merely try to keep it under control and not let it explode.
I can't remember using emojis in the SE communities that I belong to; if I have, this must have been 1-2 times a year. This said, I do believe that using them is a matter of personal style that expresses one's personality: some of us are dryer, some more colourful, some quiet, some bubbling etc. I would discourage their use through my own behaviour, but never edit a post to eliminate them. If somebody edited my posts in order to remove them, I would intepret this as an aggression and definitely roll back (I have done this twice when a final "Thank you" was removed for being considered "noise").
Finally, the core issue: some people seem to believe that greeting, thanking and emojis are "noise"; this scares me. The internet is no longer some tool (like a refrigerator, for instance); no, it has become a huge part of our daily lives, and as such it will be more and more imprinted with all the characteristics of the human psyche. This is healthy, natural, and as such we shouldn't try to repress it.
(I find it funny how many in the developed countries try to be more and more "inclusive" (and "nice", as seems to be the latest fad on SE), but at the same time are looking for what to exclude next: now it seems that it's emojis' turn to be excluded from our inclusive world.)