There are some rules for when this happens and when it does not. Don't know what they are exactly. Maybe the camelcase in GitHub may have triggered. Anyway, as you say, afterwards you can edit the title and give the desired case format.

It is title case: https://en.wikipedia.org/wiki/Title_case

I first interpreted it as a puny way to advertise some improved github issue tracker

I also find myself writing titles in a "Title Case" like that. It is a habit I got from the days when I used to blog.

BTW you can see changes that occur like this on https://hackernewstitles.netlify.app/ - it seems like the automated title casing is being overridden by mods later on, perhaps.

From what I can tell from looking at older submissions, it might be doing it if the title is 4 words or less. Not sure why that would be the case though..

Too much smarts in the wrong places imo..