It would be up to Lemmy developers to implement flairs, and then the Mlmym developers to make them visible on the interface that is displayed when you go to old.lemmy.ca
. If we (Fedecan) were to try and implement something just for ourselves, it wouldn't be that helpful since only our users would be able to see and set the flairs.
It looks like post flairs are on the way though! I see this merge from last week for "finish adding post tags"
https://github.com/LemmyNet/lemmy/pull/5869
Referenced in this issue
https://github.com/LemmyNet/lemmy/issues/317
User flairs will likely come later, but it's planned from what I can tell. The issue was kept open:
https://github.com/LemmyNet/lemmy/issues/1456
Having the flairs be displayed in the old
interface may take some time, since that project seems to see slower development. If someone has experience in the 'Go' programming language, they can help implement it to speed things up