When a big emotional upset is involved, it is important to separate the faulty math from the real evidence. They could claim millions of dollars in loss and it still wouldn't change the fact that they were stolen from.
The template is nice, but I've seen templates like that before. It's clean and well done, but to be honest, it's not that unique either. That little ribbon on the dark background - I have that on my website. The class "plusIcon", I probably used all possible permutations of "plus-icon", "plusIcon", "plus_icon", ... somewhere over the last couple of years. The color is the same, but hey, the number of colors is somewhat limited. And then the html differs as well if you really look at it. The CSS differs significantly.
EmailOnAcid acknowledge the inspiration they used for a mostly educational article, and promised to change the design in the article. Now that could have been a peacefully and entirely fair resolution for the problem. Another option might have been for EmailOnAcid to acknowledge the inspiration and link back, offering the opportunity to rack up some sales to offset the damage.
But now the case has been blown out of proportion - they created a new blog to post this entry(!). I understand the feeling of rage, but that's not a good mood to write a blog article. And for me, personally, stampready just lost out. I'm not going to buy from a company that goes ballistic at the first possible opportunity - I prefer to deal with professionals.
My point is that the whole article smells of "we wanted to be insulted", name calling and call to action included. Writing a blog article to call out copying is the nuclear option, setting up a blog and writing a single article, just to play the nuclear option is just not warranted over such a minor case.
As far as an extra space, it seems very plausible that whatever editing process resulted in a single extra space at the end of a line could have happened to two developers. I know in my own code, and I'm usually very careful, sometimes I end up with extra spaces that I only catch via diffs. If the "typo" had been something like "plu_s_icon", that'd be much stronger evidence.
The result is much like you'd expect for someone copying the design (i.e., looking at the template and saying "we can do that"). It's possible someone did copypaste it, then changed the HTML and CSS, but that isn't what they're claiming.
EDIT: I apologize for going against the popular opinion on HN.
A. "Ah, I've brought up a politically charged tangent and people are downvoting to keep the discussion on topic"
B. "I'm a martyr to the HN hivemind!"
Yeah, definitely the second one.
This silly algorithm for calculating damages is irrelevant to this claim of theft,
is not the same as saying:
All claims of theft from everyone who uses this silly algorithm for calculating damages are equally true or untrue.
Apologize for the failure in reasoning and the passive-aggressiveness instead.