Emoji’s current require a space before the colon in order to be recognized:
Hello world:smile: (no space before emoji is NOT OK)
Hello world! (non-word character before emoji is OK)
Hello world (space before emoji is OK)
Hello world (no space after is OK)
It is a little cumbersome to always have to remember to type a space before adding an emoji.
The situation is less of a problem in most languages because of punctuation and words being naturally separated by spaces.
However, for some languages, such as Chinese, which has no spaces (and before the turn of the 1900’s, no punctuation – which was a Western concept), it is very annoying. I’ve seen many users forgetting to put spaces in front of their emoji’s in their Chinese posts.
My suggestion is to always add a space BEFORE any emoji that is inserted via the picker, UNLESS the previous character is a space.