I'd say that a relatively small number of my fellow setters visit the forum, and when they do so it would typically be when they have had a puzzle published and they want to see how solvers are getting on with it. Quite often we wish we hadn't looked!
If you want your feedback to be seen by the setter, I would suggest that the best place to post it is as a comment on the appropriate blog - for Telegraph puzzles, Big Dave's site (
http://www.bigdave44.com); for Times puzzles, the Times for the Times site (
https://times-xwd-times.livejournal.com); for Listener puzzles, the Listen with Others site (
https://www.listenwithothers.com); and for other puzzles (eg Independent, Guardian, FT), the fifteensquared site (
http://www.fifteensquared.net).
If you want to reach setters in general, your best bet is the Crossword Centre message board (
https://www.tapatalk.com/groups/crossword_centre) - this tends to be frequented by the less radical setters (ie you're not likely to reach most of the Guardian setting team through that route).
If you are simply worried about setters reading your posts on the forum and attacking you in the street (or elsewhere), there is no need for concern - we are a thick-skinned bunch ;-)