I would imagine that it is relevant at least in that it shows that there are different perspectives regarding what constitutes an acceptable solution to the use and restriction of reward points.
You believe that Sideshow is, in some way, responsible for your loss of reward points, since the online system didn't alert you at the point of sale. Jedibear believes that the information published, both in the newsletter and in the PPO notice, was more than adequate, and that you would have been sufficiently informed, had you read the message in its entirety.
To be fair, your point has some validity. Sideshow could make their point of sale system more "bulletproof". But the question remains, who is more at fault for your loss, Sideshow or you? You asked the question, "who reads the whole newsletter?" The answer should be, "anyone considering placing an order with Sideshow Collectibles."
Referring to the terms and conditions as "fine print" is slightly disingenuous, since it isn't in any different typeface or font size than any of the other information, either in the newsletter or the PPO notice. And, in the notice, it is preceded by a "PLEASE NOTE:" heading, which is bolded and in red, and the text of the restriction itself is also bolded.
So, could Sideshow have done more to protect you from yourself? Yes, they could have. Are they at fault for not having done so? I don't believe they are.