Ok, so it depends on stage.
Something that has huge effect on bigger user bases are feedback loops (just a menu option for Give Feedback) which can be massive. We had a user base of 120k when we implemented that (first thing I did when I took charge of the product) and we got over 2k feedback notes in the following year that allowed us to improve so much we grew to 200k users.
For smaller stages, there is no replacement for giving everyone direct access to you. Just the good old call and email asking, how are things and can we help you with anything, to get the conversation started.
You can simply invite people from LinkedIn in their fields to go for a beta test and then have them write their review in return for giving them a year or half a year subscription.
My gut feeling is that it's hard to get critical feedback on Product Hunt. But saying that, I'm thinking about useful discussions that could work here.
On other mediums, including links to forms and having direct message communication with people is very handy... especially for early-stage products.
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