I am a fan of referral codes because who doesn't want to earn some extra altcoin during the ICO. However, I've noticed tons of people sharing their referral codes for the ICO they are supporting by posting it on the ICOs official thread or telling people to send them private messages. Is this practice allowed? What threads is this banned from?
No, putting ref links into your posts isn't allowed by forum rules. There are some exceptions, though.
For example, there are websites which allow new sign ups only if you are "referred" by another user. So, in such particular cases it's okay to put ref links.
Also, you can put ref links into your signature space.
Also, after watching videos / reading articles by other people regarding an ICO sometimes you will see people spamming the comments section with their own referral codes (fortunately most sites allow you to delete comments, but others won't). This drives me mad because the OP / author did all the work (either to shoot the video or write) and all these people are trying to take advantage of a work they didn't do. Do you think this is correct?
Not only it is not correct to the uploaded. It is also useless. These people who spam their ref links in to the comment section of youtube videos are just wasting their time. No one will click on their links and many people will pass on as soon as they see the referral links. Very stupid crowd.