Read state may be incorrect with pre-emptive moderation

[glebm]

If posts from new users are not visible until they've been moderated, then it is possible that a post will be considered read when it hasn't been read yet.

Consider a topic with 3 posts:

1. post
2. post: invisible, not yet approved
3. post

A user visits the topic.
Then, post 2 gets approved.
Post 2 will be considered read for that user.

Related: #524

[timdiggins]

I think the situation you describe is tricky to resolve and will always be a compromise.

I would prefer to think of the Topic as having only 2 posts until the 3rd post is visible.

So before moderation:

post #1
post #3

And then after moderation

post #1
post #3 
post #2 

So we render post#2 as having been written "after" post#3. (which means we are privileging posts which are moderated early (or by pre-approved writers) over posts requiring pre-moderation. This seems right to me).

However to make sense of this for readers (and the pre-moderated post writer) we could possibly add "publication delayed (by xxx hours) by moderation".

To implement all of this we would need a new field "visible at" which we use (rather than created_at) for ordering and comparing with the read_at of the read state. We could still show when it was written in the UI.

[glebm]

Alternatively, we can have a table of (user_id, post_id, is_read), but it's not very useful until we have some UI indication of the read state of an individual post.

So I'd rather just ignore this issue until then, if we decide this is the way to go.

However to make sense of this for readers (and the pre-moderated post writer) we could possibly add "publication delayed (by xxx hours) by moderation".

Whichever solution we go with, this sounds like a great way to reduce confusion!