Perhaps I should further specify just what sort of spaces I'm clear and unclear on. (All "maybe"s, "probably"s refer to my own uncertainty, of course - for simplicity I'm doing writing this as if I hadn't read any of the cousin posts yet.) The examples listed here are whatever I think of, mostly relevant ones but not all - I don't think there's a zoo anywhere around here and I haven't been to one in quite some time, but the example occurred to me while I was writing this so I threw it in. I expect I'm right about the things I'm certain of but should that not be the case corrections would be appreciated!

1. Definitely OK to approach people: "Private public spaces" - anywhere where a person you don't know can be assumed to be a friend of a friend - small parties, common rooms in dorms or co-op houses

2. OK to join existing conversations, maybe not OK to approach people initially: "Purposed public spaces" - anywhere where a person you don't know can be assumed to share a common interest - a common room in a school department building, e.g. Game stores probably fit here too. Also probably competitions of any sort.

3. Probably OK but currently avoided by me: Outside - on the street, on the quad, in the park. Here the location doesn't let you infer much of anything. (Unless something unusual is occurring, then clearly OK as people gather around it.)

4. ???: Fast-food places or food courts. Non-quiet spaces where people go to get work done (but which are too general to fall under #2.) Zoos, museums, other similar places. Bookstores.

5. Probably not OK: Libraries.

6. Definitely not OK: Anywhere where you shouldn't be talking in the first place. Most restaurants.

Again, thanks! The sibling posts have already clarified things some.