[eynsham]

Most important legislation, including the BNA, is government legislation (indeed, see the white paper: https://www.uniset.ca/naty/maternity/wpaper.pdf). It is therefore drafted by parliamentary counsel, whose advice remains available when amendments are proposed. Most governments also command sufficient majorities to push this kind of legislation through, or at least to come to consensus on amendments. The relevant passage seems clear enough that parliamentary counsel could have drafted it and so I doubt there were ‘too many chefs’ as you put it (although I haven’t checked Hansard).

It is also hard to see what these drafting habits have to do with the common law system. Points 1–5 could be true of a legislature in pretty much any legal tradition.

[MrJohz]

Moreover, the HoL and the "ping pong" process actually gives the legislation a chance to be refined, as the lords are less motivated by party politics and more able to focus on getting good legislation through. I've heard a number of complaints about the current system that basically say that without the HoL, the quality of legislation would be significantly poorer, and that there needs to be more work done on getting bills written properly in the first place when they get proposed in the House of Commons.