There is a Stack Exchange community for code reviews: https://codereview.stackexchange.com/
However they have some strict rules on what is allowed so it may not be suitable for open source projects. Two problematic ones are: 1) The poster must be the author/owner of the code. You, for example, can't post code that someone else has written. 2) All code that is to be reviewed must be included in the post. You can't just link to a repository.
StreetComplete uses OSM's built-in note system to leave the notes, so basically any OSM user can see them and react to them.
I use Vespucci now and them, but most of the time I find it too fiddly to use on the go. What I usually do is also have OsmAnd open and use its own note system to make a local audio or photo note. And when I'm home I go through the list of notes and change the things in ID or JOSM.
"If you have one"? What's the point of that insert?
My guess is that isn't a cycle barrier at all. For me it seems to be a special form of removable or foldable bollard for blocking two track vehicles but allows emergence vehicles to open them.
There actually is a Stack Exchange community for code reviews: https://codereview.stackexchange.com/