I'm snarky enough to wonder if the reason he attached a warning icon to the book is that it's only available in Kindle format and for people who will tolerate DRM. But it's early and I'm snarky, so don't listen to that part.
Seriously, Robert, instead of thanking us for reading your post (that looks weird from anyone older than 10), making your book available in a format we can read would be a huge help. Saying "it can be viewed via free software on your iPhone or on PC" doesn't do it. Aside from the fact that MR members are, by and large, smart enough to know about how to read our e-books, we also generally don't
want to read them on computers. If we did, we wouldn't have bought ebook readers, and therefore probably wouldn't be here. All the thanks in the world won't make up for not having usable formats, and despite what Amazon says, .mobi is only one of many formats. You're denying potential buyers the ability to use the book.
Things MR readers will readily buy: DRM-free books in multiple formats sold for $3 or so.
Things MR readers will buy a lot fewer of: DRM-encumbered books formatted for a reader many of them don't own, sold for $6 or more.
You can sell whatever you like, of course (and even use warning icons!), but if you're trying to sell DRM-loaded Kindle books for paper book prices, you're going to be leaving money on the table. Maybe it's just me, but I'd want the money instead of whatever pleasure those choices would bring. I'm greedy that way.