Aha fair enough, but yeah browsers often allow invalid HTML to just work. But that doesn't mean that the valid usage is somehow flawed. I can understand that th

Aha fair enough, but yeah browsers often allow invalid HTML to just work. But that doesn't mean that the valid usage is somehow flawed. I can understand that the dash can be a bit of a weird rule if you're new to HTML. But I think it's an elegant way to allow users to create custom tags and have readable compact semantic HTML. But yeah I also do see the confusion part, if a person new to HTML sees these custom tags being used it might think it can create one too and not realize it must contain a dash, and it would still work. So yeah in that sense, indeed it's confusing if you're unfamiliar with it. But having multiple </div></div></div> at the end of a large block of HTML is also confusing, often resulting in closing too many / too few divs. Having </nav-item></nav-bar></main-header> is much better. So yeah it has it's pros and cons I guess.