The post with database schema lists "31 = Comment discussion moved to chat" as a possible PostHistoryTypeId.

Strangely, when I try to search for such posts from SEDE, I get no posts on Mathematics and a single post on Meta Stack Exchange.

Indeed, when I take a post where comments were moved to chat - like this one: skeptics.stackexchange.com/posts/44625/revisions - and check what I get in PostHistory table, this event is missing: data.stackexchange.com/skeptics/query/1252003/…

Should this be considered a bug? Is it worth reporting?

@Martin the difference is that the skeptics one is "Mod moved comments to chat" that is a different event then the "Comment discussion moved to chat". The latter can be generated by 2 users going back and forth 5 times in comments. The former is only triggered when a diamond clicks a button.

Ok, so 31 is not a mod action, it happened automatically.

Still, it seems difficult to believe that this never happend in the history of such a big site as Mathematics. Maybe there is something wrong with my query?

yeah, even on SO there are none: data.stackexchange.com/stackoverflow/query/1259825

something is weird

I see that on Meta Stack Exchange in the revision history of the post which was returned there is: "Comment discussion moved to chat". As opposed to "Mod Moved Comments To Chat".

I think it is worth to ask a question on Meta about it.

So it seems that "Mod Moved Comments To Chat" does not have a PostHistoryTypeId.

yeah, I think they are careful with adding Mod actions into the easily queryable data

Some mod actions are there: data.stackexchange.com/meta.stackexchange/query/890114/…

fair point

I was pretty sure this was dicussed in the Tavern at some point

that answer seem to confirm that.

That query is based on comments (rather than revision history).

Nevertheless, it seems that "Comment discussion moved to chat" isn't actually recorded in the revision history (or PostHistory).

What you could do is use the comments to find "moved to chat" comments, then hand check their timeline / history .

to further support your case I mean.

@Martin there is literally just one data.stackexchange.com/stackoverflow/query/1259844 across all sites ...

I formulated it as a feature request: Moving comments to chat seems to be missing in timeline and SEDE?

Although I was mainly motivated by a curiousity.

Originally I wanted to add PostHistoryTypeId=31 to the query listing the mod actions. (The ones which are publicly visible.)

I simply misunderstood and I though that it was standing for moving to chat by a moderator.

Since I did not see any such records, I started to investigate a bit more.

Thanks for your help!

no problem!