(partially) revert monitoring for impossible disconnect

[Aras14HD]

In #318 I added monitoring on the suspicion, that we were missing some comments. This was not sensible, everything it has caught are false positives, where the "canary" comment was deleted and one new comment was posted.

I now checked and confirmed, that the query "before", that we use is immediate (always gets the next comment, no matter how many comments there are), so no comments can be missed by us.

I kept in the log for losing that connection, but as info, because it is an external thing, when people delete comments.
For the same reason, I made thread id densification failure only info when the thread id is just an empty string, and made the likely harmless "Missing ratelimit" info as well.

Also added a warn for when we actually reach capacity, indicated by getting COMMENT_COUNT responses. And took the opportunity to add exeptions like for status 500 for further server errors.

So mostly making the log cleaner/less cluttered.

[Aras14HD]

I also would want to make the polling for comments message debug, as it is way too common (so much so that we filter it out and ignore it)

[tolik518]

debug makes sense to me, as you have mentioned, it's something we don't usually want to see, but sometimes I still find it helpful to see a heartbeat