I've tried leaving a few comments on his blog, but they never show up.

I'm not certain if this is correct, but someone once explained that the boys have to read the comments before they appear. I think it makes sense, since Yanagi's posts usually get upwards of thirty comments (except for his last two posts, but presumably he's busy with 'Cooky Crown' and 'Puzzle' Promotion) usually while the other boys have none.