Referrals generate small amounts of revenue for people that post them if people buy using the links. With Amazon, it is easy to do it on accident. With most sites it has to be done intentionally, so when people see reflinks they think you are intentionally advertising for profit.
The reason that is looked down on is because some people would just spam reflinks to make $ and not to actually share gear they own, and then the forum would be more spam than conversation from real owners.
I know in your case, you are just sharing gear you do own. For example on your knee guards this is the reflink post:
https://www.amazon.com/dp/B07F8NB7CP/ref=cm_sw_r_cp_apa_i_y97JFbY3GNE10?_encoding=UTF8&psc=1
and this is the exact same link, and it works exactly the same, but with no reflink.
https://www.amazon.com/dp/B07F8NB7CP/
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So if you don't paste the ref portion, it still works. Amazon makes it easier to accidently include reflink by including it by default so I believe you that you did not do it to advertise, but most people see reflinks and downvote by habit. So I am only telling you so that you don't get downvoted on future posts. If you don't post reflink I don't think people will downvote you.