Also, having a conversation is pretty much impossible if there are a lot of comments, mainly because the comments are linear. If you want to catch replies to your comments, you need to read everything or search for your username (hoping they included it).
I always hoped that Mefi would go threaded, but the current way is clearly the desired mode. It's also the reason I don't really look at the comments on Mefi anymore.
Metafilter comments sections are still very often worth reading, but the lack of threading means the conversation is always moving somewhere, and going back to reply to someone 15 comments up is less likely. The upside to this is that it favors newer comments, unlike reddit/hn, which favor upvoted comments (which are often the oldest).
I prefer linear comments. I have four open tabs with Mefi posts in them right now. Every once in a while I will reload the tabs and I can easily see what was added since the last time I refreshed.
With nested comments I have to go back and dig for new stuff. This is why I read the comments on HN, Reddit, and slashdot exactly once unless I added a comment and want to see if there was a reply.
I always hoped that Mefi would go threaded, but the current way is clearly the desired mode. It's also the reason I don't really look at the comments on Mefi anymore.