There's a popular piece of "newer" software that decided that XML rules were too difficult. So they URL encode all values. It also uses print style formatting f

There's a popular piece of "newer" software that decided that XML rules were too difficult. So they URL encode all values. It also uses print style formatting for XML tag names, so if you manage to get a name value that has, say, a : in it, you'll get invalid tags. This is the default setup, in 2016, for a system that handles a lot of real-world telephone calls. Even just a few years ago I've worked with companies that wrote their own "XML parser". They explained it was pretty easy but they had to "special case" for broken output in the real world. An example of this output? "<tag />". HTML would have been far better off if it had the strictness of XML. Remove end tag names so you can't have invalid nesting. If browsers had refused to parse invalid docs from the start, invalid docs would not have been produced. (And like XML, they could provide decent error messages, so the difficulty would not be significantly raised.)