Is this a known issue? If you type in 
somewhere it will be replaced by 
Don't get me started on how this messes up linux commands and scripts, Is this a me problem or a lemmy problem? I need to study, if this is a known problem, then fine, but if it isn't then it needs to be reported.
"standard" is that the character you input stays as the same character and isn't transformed. The fact that it's being shown as & means that either OP is using a client which isn't correctly decoding html, or its being double sanitised as &. Neither tog those is "standard", it's a bug.
Not in HTML. Never has worked that way.
Special reserved characters have always been handled this way because you don't want to accidentally interpret something the wrong way.
Same for URL encoding. You upload "Clever Name.PDF" to a website and it generates a URL of "Clever%20Name.PDF" because spaces aren't valid in URLs. %20 is the code for a space.
But when you see it on your screen it's supposed to be converted back into the actual character, otherwise it would be pointless. So if you're seeing & then the website is messing up.