I'd rather not have to run a scene as an AMPC or even communicate something to a player in tells to clarify, only to find that the player in question has no tells turned on, and suddenly I have to do the arguably more immersion breaking thing of //Etcetcetcetc instead.
By far, the
vast majority of the Tells I receive are from players I am not in a scene with at the time. Frankly, I don't really experience that much need for clarification when I'm actually RPing with a player. If there's confusion, then RP the confusion
People misunderstand one another IRL.
Likewise, if I prefer not to receive Tells, I don't think another PC should have the right to inflict Tells on me simply because that PC is unable to express the RP ICly.
For the sake of argument, however, let's consider whether // is "arguably" more immersion breaking.
Case 1: The AMPC (or whatever) is interacting with only one other PC. Then there is no substantive difference between the Tell and the //.
Case 2: Multiple PCs are present. Then whatever confusion has arisen would seem likely to be confusing to all those present. The Tell, in fact, informs only one PC of the clarification, as though by telepathy, which invites cheesing. WYSIWYG, after all. It would be much less disruptive to use // to clarify for everyone all at once.
Regardless, and even given there may be some cases in which Tells are--as I concede--a necessary evil, players should not have to be subjected to the far greater number of cases when they do nothing but break immersion.