apt modernize-sources apparently discards comments found in apt source list files, which may be notes for humans or temporarily unused data sources. They should be retained as comments.
As it's the pattern used in there. Thank you. source
Control: severity -1 wishlist We are aware, we do not have access to the sources.list parser state, only very processed objects further down the stack. But even with access, comments are complicated, because you now need to associate the comments with entries.