The RNN does in fact directly predict emoji. It outputs a vector of length 1624 (the number of emoji) containing the score associated with each emoji given the input text. This vector of probabilities is what can be though of as the point in semantic space.

The issue of multiple meanings is that if you strongly predict an ambiguous emoji (say the prayer emoji) how do you then extrapolate what concept is contained in the sentence (e.g. was the person saying "thanks" or "high five" or "please").

[I'm also a Dango dev]