Why are headers limited to four levels? Do they have to be always padded with spaces? Why are references limited to one symbol? It can just be more mnemonic to

Why are headers limited to four levels? Do they have to be always padded with spaces? Why are references limited to one symbol? It can just be more mnemonic to have `java_doc` than `j Why only full reference links are allowed? It would be handy to have a shortcut for links without reference, and it's not like we're running out of symbols: `?[]` could be used for links without reference while being consistent with `![]`, which is used for transclusion Why is it impossible to put backticks inside a code span? What is there a `<!-- -->` in an example in the Lists section? I really like the spirit of this markdown alternative