Good contribution @Bastien_Siebman.
Personally I am not very loving emojis in task managers. Maybe it’s because of a form factor, I mean, I love emojis but to communicate in messaging applications.
For professional environments, they are a great visual aid, but I get a lot of variety of shapes and colors.
Maybe I would think differently if you had the option of putting linear icons.
The only symbols I use in asana are star-shaped characters to indicate the level of concentration that some tasks may require.
A pleasure to read you
Greetings from Barcelona and best wishes for 2020