Only consider in-group. That means add reactions to the events to be loaded for all profiles that have degree < 100 and load reactions only from local IDB.
Show up to 5 most frequent reactions (3 :+1: 3 :100: 2 :heart: ... 15 reacted) on all notes
Show reactions like GitHub does.
Show only the last reaction of each user that reacted
Reacting should be possible like in GitHub, with a limited set of relevant emojis