Hmm, a quick look at the html on the logged-out view of a post with lots of comments shows no sign of a meta robots tag, so the pages are technically crawlable. this one
But it looks like only about 25 comments out of 439 are in the html on that first page view, so probably only those will be picked up by a crawl?
Yeah, it’s made more for refining and confirming details than for adding entirely new objects.
When I want to add something that’s not on the map yet, I either add a note in StreetComplete and come back to it later on my computer, or I add it using Vespucci. (I’ve been known to add items using Vespucci, then reload the data on StreetComplete so I can fill in details that aren’t in the presets and that I can’t remember how to tag manually!)