I wrote this in a comment earlier today, but it deserves it's own post:

Many theorists are failing to take into account something of
staggering importance. No actor has known that they are (or will be) Red
John until the very final episode of RJ with the reveal, which was
recently filmed. THEREFORE, every single voice recording we have of RJ,
and every single sneak-peak of RJ (be it in a mask, or holding a cup of
tea, or in the shadows) has been using an EXTRA actor (or a voice actor)
with no intention of them being RJ ultimately -- just to film a
specific scene for purposes of the show. THEREFORE --- we can not, ever,
take into account what a voice sound likes, what a hand looks like,
what a body shape seems to be, what a shadow looks like etc... from
previous episodes. It is completely false information. The show (Heller)
has been abundantly clear about this in interviews etc. So, please
disregard all evidence of voice samples and the like. They mean nothing.