To me, that doesn't sound like your analogy at all. It'd be true if the extension for example redirected an HN thread to a reddit thread of the same posted URL, ie a replacement of the original, but the extension simply adds features to the existing site. There have been extensions like this available for years, like Refined HN which this is based off, as well as many third party HN clients. Therefore I think you should try it before judging so harshly.