I had a feeling they shuffled comments randomly a few times during the first 1-2h after post creation. But I guess you are right, it's easier to get noticed by bandwagoning the most popular comment.

Maybe if there are a lot of comments - display five randomly chosen and get those up/down voted first before showing everything else?

But there would still be a problem with some just having longer lifetime hence higher chance of being in the top than others.