> This is nice enough. But the point is: it requires JavaScript (React, 3rd-party-tooltip-on-npm, your JS code) before anything will render in the browser. It’s an all-or-nothing approach.

As was already pointed out in the previous discussion (of the previous blog post) here on HN, this is a complete non-issue. In most frameworks these days you would prerender your application or maybe even server-side render it.

The issue I see with the suggested "solution" (of the non-issue) is that the "placeholder" <img> tag is not "type-safe". I can put anything in there without paying attention to what exactly my web component does or expects. If the behavior of my web component changes, I won't get a warning at code writing or compile time. Instead the layout will silently break.

All in all, I don't think this approach scales well with the size of the code base and the number of people working on it. (Let's say, e.g., <user-avatar> is provided by some other team.) And again, it's trying to solve a non-issue.