Too many reaction emoji!
Proposal
When clicking "add a reaction" one gets a rich choice of many many emoji.
It's great, and one wonders why didn't the Facebook and GitHub people think about this, with their dumbed down set of five or six emoji.
Well there is good reason: users want a small standard set of basic emotions! It standardizes communication and doesn't leave users guessing meanings, no matter the writer or reader.
Therefore, please have a two-tier system: The user can either pick one of a small set, or go on to pick one of the extended set (so as not to disappoint current users.)
Sure, "they can just find the standard ones they want, and after using them a lot, they will rise to the top line above the rest." Well yes, but that still makes the user responsible for hunting which standard ones should be standard for him... but I am talking about GitLab-wide standards.