It is understandable and reasonable that when someone believes someone else is breaking the rules in their favorite game, especially for monetary reasons, that they may get upset, and even post about it.
At the same time, it's weird when some convince themselves that Blizzard would create a policy making the sale of leveling guides that can load into a free addon against the rules, and then immediately ignore the sale of leveling guides that can load into a free addon. The reason this is weird is because this is not what the policy is for or what it says. Selling the guides is not some sort of loophole that Blizzard, with full knowledge of how leveling guide addons work, couldn't have closed if they wanted to. The fact Blizzard doesn't pursue it is evidence of how they're interpreting their policy and that they didn't write it with intention to stop guide sales.
As it pertains to gaming guides and the WoW UI Add-On Development Policy there are often misconceptions about it that create a lot of unnecessary conflict between players and creators. I'm here to clear up those misconceptions.
First the foundation - it is very easy to find information about the Brian Kopp vs. Blizzard (Vivendi). If you're not familiar with this, look it up. There is also Nintendo vs. Prima Publishing. In general it is well established that authoring gaming guides, and then selling them, is considered fair use and defensible.
It is not illegal to author and sell a gaming guide, the same as it's not illegal to author, publish, and then sell a book.
It is not illegal to create a proprietary format to store your book. This should be obvious. Amazon does this every day with their Kindle ecosystem.
It is not illegal to create a reader for this book.
It is not illegal to sell books in your proprietary format with intent that the books can then be read using the reader.
It is not against Blizzards EULA or the WoW UI Add-On Development Policy (different documents, btw) to develop an addon that is capable of reading and displaying the contents of the proprietary book format you invented.
A book is not a feature or a service being provided. It's content. Just don't use the addon to advertise that the book is for sale. Blizzard doesn't want addons that spam users with ads, or charge money for a version of the addon that won't spam ads or unlocks other features and you're good to go.
TLDR; Addons that have the capability of having data loaded into them are allowed and always have been. Selling data that you created or selling public data that you've compiled is not a legal loophole. Data isn't a feature. Data isn't a service.
It's also not game breaking, creating an exploit, disrupting the player's experience, or causing server issues, or creating a situation where a player might feel compelled to pay a ransom for a set of features that they feel like they're losing at the game if they don't have it... of which that short list are the things that Blizzard created the rules to prevent.