I completely disagree that comments should be called out in bold because they are supposed to add important information. Even in code where that is the case, they are still just metadata. Comments are there to help you understand something. Comments should never be shouting at you, drowning out the code itself. We only have so much attention to spare, and most of that attention should be focused on the actual code, not the comments.

The biggest danger of comments (especially in heavily over-commented code) is that they can be misleading. If you get over used to relying on the comments as a true indication of what the code does, it's easy to be misled. It can especially cause you to miss subtle errors in the code (like an = instead of ==, or > instead of <).

Your eye should be drawn to the code first and foremost. Hence it is most important that it is formatted neatly and really, syntax highlighting is just a good way to catch typos quickly.

Comments should be what you read second, not what you read first. I.e., I just read this bit of code and it seems a bit weird, so I'll check the comment - oh yeah, now I understand what it's doing. Most comments should be ignored most of the time.

"we have collectively decided that the comment is less important than the code" - this is simply because the comment is less important than the code. Comments are not necessarily correct and don't always accurately represent what the code does. The code however, is always 100% accurate. That's why experienced programmers rely on the code first, comments second and try to avoid commenting ideas that can be expressed equally well in the code itself.

The use of Javadoc style comments is another strawman. As much as we might wish it were not necessary, using comments to generate documentation is actually useful. Similarly, having a coding standard requiring a comment block per class/function for the docs is also useful. A standardised structure is helpful when reading lots of code, and it helps delineate long source files, even if many of those comments turn out to be redundant. Having a highligher scream about all those comments being super important isn't helping by making people write more concise comments - it's merely trying to solve a problem that doesn't exist and creating a new problem in doing so.

Sometimes I need to comment something that really is super important like the example in the OP. It turns out, there's a way to do that which doesn't even rely on having any syntax highlighting whatsoever. You just write your comment like this:

// !!!!! IMPORTANT WARNING !!!!! //
// This does something really dangerous,
// so don't change it unless you understand it...
// !!!!! BEGIN CRITICAL SECTION !!!!! //
if(foo) {
bar();
}
// !!!!! END CRITICAL SECTION !!!!! //

I write code that needs something like this maybe once every 6 months. Do I want every single comment that I write called out with equal importance? Nope. Is limiting comments to only comments of such dramatic urgency a good idea? Also no.

A related rookie mistake that I see a lot is conflating the idea that less code = less complexity. Inexperienced programmers like to cram as much logic onto one line as possible, whereas better programmers often write the same thing as one-statement-per-line with a bunch of temporary variables, whose name encapsulates what each operation is doing. Which one do you think requires several lines of comments to explain what it does, and which requires no comments whatsoever? One has less code, but both have the same complexity. Except the one with more code breaks that complexity out into smaller, less complex individual chunks which makes reasoning about the whole much, much easier.