"The web interface to the version control system doesn't parse the here-string correctly" isn't really a criticism of the PostgreSQL extension. It's a bug in the syntax highlighting.

The COMMENT feature isn't even a good choice for a VIEW, PROCEDURE, or FUNCTION, each of which already supports comments inline in the object definition on the server. No, the main benefits are adding comments to objects that DON'T retain them, like a TABLE, COLUMN, CONSTRAINT, ROLE, etc.