TLDR; spent half year building a product and launching it and tried to just post a white paper here on HN and reddit to get some feedback: instant ban for self promotion. From what I've seen, it is not even clear that humans are involved in this process. So how should I proceed? Start paying for ads?
You have to slowly engage with the community and use it or a regular but even then you are not supposed to self promote. What you can do is ask for peoples opinion of your app.
It seems that there is no clear definition of what self promotion is. For example, sending the security and privacy white paper of my product to r/privacy and asking for feedback was seen as self promotion.
Reddit is banning accounts so frequently. I would suggest avoid posting anything for the first week of account creation, and even when you post, do not add a link. unfortunately the only way for startups to promote themselves now is to do shadow marketing.
tbh, its worse than that. This one time, I used to post to reddit, without adding a link, and some guy from competition used to reply to comments of people who used to ask for the tool name and link. haha basically i sow the crop and he reaped it.
i ran into a similar issue when researching how to get my project off the ground. the key is having an aged account with karma and being open and honest about you building the product instead of attempting guerrilla marketing.