Is ノシ considered 絵文字? My friend ended a letter thusly: > symbolizes a waving arm. Is this considered or does it have a different name?

Nico Nico actually calls it . (And so do other places like here.)

**Edit** : There is, perhaps, some crossover, but more broadly refers to things like pictograms (pictures with meaning), while refers to...well, (characters put together to make faces).