Out of sight out of mind

[Dicebot via Digitalmars-d]

Big problem with GitHub issues is how simplistic those are. All 
categorization is done by labels with no internal 
differentiation, advanced search queries are not possible. Also 
bugzilla is self-hosted solution we have full control about and 
with GitHub you can only rely on what external API exposes.

Also consider effort needed for moving all issues from existing 
database and breaking routine workflow of all active dmd/Phobos 
developers.

Personally I don't think this is as much of an issue. Issues 
don't get much attention because there are only few people 
looking at them (other than own issues). Most D users don't have 
any reason to do so.