Grabbing all the comments and intelligently displaying them in a terminal would require substantially more work, I suspect.
Right now, I don't see why I should use this tool when I can just use elinks.
elinks -dump news.ycombinator.com | sed -n -e 's/\([0-9]\+\)\.\ \+\(\[.\+\]\)\+\(.*\)/\1: \3/p' | grep -f words.txt -iEDIT: Though I suppose it would be cool if comments worked, too.
I know that the effect can be achieved by running an NNTP server, and using a mail/news gateway, but that's a lot more complex. Most NNTP servers are meant for big multiuser situations, and that makes configuring them complex, and often requires a lot of supporting software. Massive overkill for someone who just wants to read their mail in their newsreader and get a good threaded message view with a good UI.