Well, to be fair I think “share” kind of implifies that others might be able to see it
In my opinion another pop-up box everytime one want to share a variation would be rather annoying while kibitzing or sharing quick thoughts on an ended game.
But rest assured anything you do (chatting or sharing variations) is invisible to both players until the game is concluded (only other observers can see it) which I think is the main concern about this.
As Adam said, players can’t see any other comment or variation but their until the end of the game.
So don’t be afraid to add noise to the game or to disturb players.
At worst you added noise just to the game record.
BTW, @AdamR, for that very reason I didn’t notice for a long time you accusing me to be a bully!