This is an inherent problem with web apps, since they're an app within an app. There are two different contexts fighting each other. Who's to say that Ctrl+S should save the app state or the page? Whatever we choose as the default, the non-default scenario would feel awkward when we need it.

I can think of two ways to solve this: (1) decouple apps from the browser frame or (2) use a special modifier key for app shortcuts (perhaps re-use the Windows key, e.g. Win+Ctrl+S).

See the footnote in the article:

"An exception may be if your site provides specific functionality such as in a drawing application. Even in this case it is best to provide shortcuts as an option the user has to turn on rather than one that is on by default."

Yeah. From a usability point of view, I think it's important to hijack some shortcuts, but only those who are not commonly used for such as the one mentioned in the article. I would also argue that this behaviour of blogger is not what users expect, hence it is not a bad behaviour. Wasn't there a pair of shortcuts commomly used for this purpose, Ctrl-K / Ctrl-J if i'm not mistaken?