Bartering and selling is mostly forbidden and if found to be the case they might void tickets booked with vouchers/points, all your points-miles and even vouchers associated with your account... and basically anything else on it.
They do vary from airline to airline:
Some airlines have teams on it checking forums, eBay, etc.
Some airlines don't care
Some do check sporadically about your relationship to the account holder who booked your tickets, as well during check-in they might ask.
As part of the ToS they have every right to do so, nothing you can do on your end. Some airlines might be lenient when it comes to what happens to your account, status, points, vouchers and might spare you a bit whereas others might basically obliterate your account.
Actually I am at the point where I don’t care. No avaibility for biz voucher in my routes. Have points which I can’t redeem anytime in next 3 months if I want to travel. Am planning to close axis vistara infinite poor Seat availability.