I can’t speak for the others, but Godoc is IME way better than JavaDoc, which is both hard to write, and hard to read inline due to all the f*ing HTML.
More to the point, just because some platforms provide equivalent functionality doesn’t make the GP wrong.
Have you seen the IDEs that show that documentation for the variables due to the position they take on the function call?
What is on that documentation site you linked is just a text formatting guide, it's absolutely not enough to get a powerful documentation system. But yeah, it's simple.
They provide the parsing engine with better clues for the AST that is given to the JavaDoc agent (aka doclet), which allows to customize the document generation process.
Which didn't answer my question at all. Adding more structure to the AST with @param/@return/whatever doesn't make for better documentation. It's useless crap in a real world scenario.
This is why I said it's hard to succinctly explain. Non-programmers and bad programmers can't tell the difference between Go and Python (for example) in this context. The actual difference is very very significant.
More to the point, just because some platforms provide equivalent functionality doesn’t make the GP wrong.