I just received this:
In addition to the strange character, I was wondering about the meaning (fear? speed?).
Do you consider this kind of communication a part of the language?
Would this question be off-topic on this website?
I am in favour of accepting questions of that sort, because emoticons are a huge thing in modern use of Japanese. The purist in me thinks different, but for practical purposes, I'd just run with it. Most can be answered by pointing to an online resource anyway. Which means if people google it, they find the question which quickly points them to their answer, and we don't have to keep deleting these questions again and again. Everyone's happy.
If there is even a single (answered) question on that topic and someone types a new question with "emoticon" in it, they get pointed to the older one immediately. If they insist on asking again, it can still be marked as a duplicate.
I would also not expect there to be tons of such questions, as the topic is rather narrow. As long as there are only few, it's probably not too bad.
I would say that this would generally be off topic here; however, someone over on Superuser might be able to identify what it is pretty quickly.