It is a lot less useful to read a paragraph that summarizes what R3 is about, only to find that I cannot do anything with it anyway. The less said about hashtags the better.

I would expect that if I am interoperating with implementations that conform to R4, I need to check that I don’t rely on equivalent identifiers (compatibility or canonical, depending on the normalization form used in R4) being different, but that I don’t need to normalize the identifiers I produce, because the normalization-equivalent identifiers are treated as equivalent.