Thanks, that's helpful. It makes sense that one would have to file a Form 4 for a class of shares in which one owns more than 10%, regardless of the class. Regarding the points in your second sentence, I have a question, if you don't mind (I'm trying to figure this out on my own by reading the SEC rules, but it's not very clear to me):

When Bordynuik sold his common shares while owning less than 10% of that class, are you saying he should have filed a Form 4 because: a) he had controlling interest of the company through his preferred shares, of which he owned more than 10%, and it's the controlling interest that is important, or b) more generally, if someone owns more than 10% of any one class of shares in a public company, they should file a Form 4 even if they own less than 10% of the particular class of shares they happen to be selling?