Referral links are pretty much a no-go everywhere except in your signature. There is just one exception (which occurs almost never), which is the following:
Posts with referral links can be okay if they are on topic and substantial. For example, if someone is asking what the best exchange is, and you post a decent reply, that also has a referral link that's okay.
So if you make a really good post, with pro's and con's of a service, examples of other services, etc etc etc, then (and only then) are you are allowed to post a referral link (but you must include a non-ref link as well). The thing is, 99.909∞% of the time people just make a sloppy post that doesn't contain any good information and was made purely to profit from other users.
In the end it's up to the staff member to decide if your post is relevant, contains good information, etc.
