Ask HN: Is Andrew Warner using fake accounts to falsely promote his content?

Andrew Warner's (mixergy.com) interviews frequently appear on HN. This is reasonable - the guests are often interesting and the interviews are decent. However, I'm repeatedly surprised by the overwhelmingly positive (and in my judgement, awkward) comments that are made on HN. The people leaving these comments often have very young accounts. I'm I wrong to suspect some underhanded promotion?

Examples from a recent thread (http://news.ycombinator.com/item?id=1129989):

  "Mixergy is always a gold mine for me. I get the same feeling listening to Andrew's interviews that I used to get browsing Napster for all my favorite music. I would easily pay $20 per month for this stuff."
  (Posted within a day of account creation)
  http://news.ycombinator.com/item?id=1130231

  "Andrew Warner is the Charlie Rose of startup founder interviews."
  (Posted within an hour of account creation)
  http://news.ycombinator.com/item?id=1130867

  "Excellent interview and inspiring story. Always great hearing about companies like Woo Themes who have grown organically from self-funding."
  (Posted within a day of account creation)
  http://news.ycombinator.com/item?id=1130905

  "This was the first interview I've ever seen on mixergy, and I can proudly say I'll be coming back. I thought the questions were great and I absolutely didn't mind that the video went for over an hour. Truly an indept look at WooThemes and how Adriaan was able to start up his business. Thanks for the fantastic tips and keep up the great work Andrew. And just in case you're wondering, I found this intervie from @Woothemes on Twitter (with whom I am a Standard member and own a theme from).
  (Posted within hours of account creation)
  http://news.ycombinator.com/item?id=1130539

Looking back at older threads there are more examples too. Do real people actually regsiter just to leave such comments?