Hello all! I have been lurking quite a while and I have received several useful information from several users. I was too lazy to register and post but I thought these self-isolation days are the best moments to register and post!
Regarding the discussion going on here some information I have is as follows. I am an Elite Plus and I had checked this with a couple of customer service representatives and one airport ticket office. Together with those and what I obtained from TK website, here are my conclusions about this issue:
1) %50 Busines companion ticket only applies to paid tickets in C or D class. There was a clear statement at TK website which states "%50 discount" is available only for certain classes without mentioning C or D class but this is what I learnt through representatives and the ticket office. As far as I see, this statement is removed from the web site now but I believe it is still the case.
2) %50 companion ticket does not apply for award tickets unfortunately. Companion award ticket is available at %30 discount for all M&S members (not only for Elites) for all paid tickets. That is, if you paid for a ticket, you can purchase a companion ticket with miles at %30 discount. Furthermore, the companion award ticket can be issued for the same or lower cabin.
I hope that these are relaxed recently and would be very happy if anyone has any other experience. All the best.