The Duolingo Forum is a forum to talk about Duolingo.
How to reach the forum
On the web there is a link titled Discuss. Or you can type forum.duolingo.com into a web browser.
It is not accessible through the app, but you can view and vote on sentence discussions from lessons/practices, though you can't comment from there.
Searching discussions  can be as simple as simply writing text or more advanced using operators(AND, OR). One way to filter results is by adding quotes to the search, e.g. "Duolingo wiki", and this can be further filtered by adding an operator, e.g. "Duolingo Wiki" and "lingots". For example:
streak OR lingots-> returns all the discussions that contain either the word "streak" or the word "lingots"
streak AND lingots-> returns all the discussions that contain both words "streak" and "lingots"
"streak lingots"-> returns all the discussions that contain the exact sequence "streak lingots"
(lingots AND streak) OR test-> will return all discussions that either have both words "lingots" and "streak" or that have the word "test". So, a discussion with only "test" will be returned for example.
lingots AND (streak OR test)-> will return all discussions that either have the word "lingots" or have one of the two words "streak" and "test". So, a discussion with only "test" will not be returned, one with only "streak" neither, one with only "lingots" neither. But one with "lingots" and "test" (but not "streak") will be returned.
Main article: Moderator
Course moderators are volunteers who create courses. Forum moderators are volunteers who are "considered leaders in the community and many are in touch with the team". They also ensure that users obey Duolingo's guidelines.