I would like to go digging around for which programs but it isn't worth the time and effort for my use.
You might want to read this as it talks about people getting asked about their suspicious award tickets and others, as well a legitimate use of their miles/points for booking for others:
Some of the most valuable awards are the ones you don't take yourself. Find out how to redeem your points and miles to book travel for other people.
thepointsguy.com
From the airlines partner list only for Turkish I read that they won't let you book for others if you have never flown TK. Which could be the case for forum members here trying to make a dime out of their points.
Vistara/Singapore seems to have this nominees system in place in order to prevent abuse. Even for business class and upgrade vouchers you must add them as nominees and you can only add/change nominees a few times a year.
The bottomline is don't sell your points.
Airlines have security measures that can flag suspicious activity and airline agents might enquire about bookings made in the name of third parties, I can vouch for this on AA and UA.
There's brokers online who will pay for your points/miles and for example they'll access your account, confirm the miles and do the booking on your behalf. Airlines has caught them due to the IP and the obvious redemption for a 3rd parties and suspended these accounts.
Airlines have also been known for lurking on places like eBay and some well known forums to look for people selling miles and vouchers. Either posing as seller or buyer.
Also they have flagged and reviewed accounts that are earning absurd number of miles/vouchers through promotions looking for people who are exploiting their rewards system and suspended their accounts.
Similar to banks they have systems that flag suspicious activities.
I doubt they will focus on the Indian market as to how people sell them or what they do with them as it is considerably harder to do so, but granted lots of people started using for example United due to the Magnus avalanche it will attract the airlines attention.
Don't abuse the system to book for third parties or you are likely to land in their radar. Even for legitimate redemptions they might come knocking and I doubt they'll take actions unless they see a misuse pattern. But be aware their loyalty programs is at their sole discretion, if they decide to suspend or remove all your points it's gonna be unilateral and usually final. Not much that you can do. It has been widely reported in related forums.
As for the other airlines I can't talk, you'll need to research on your own or experience it and let us know about it.
The same way banks here close loopholes or issues by lurking into this forum, or by the massive amount of people that drove people to exploit something, Iike the several wallet hacks we have seen or bugs in Gyftr. They'll notice the
unexpected suspicious amount of people when it comes to particular offers, redemptions, etc and will investigate the same.