That cannot be true because places like wix.com or wordpress.com are not penalized and they have a ton more crap sites on their domain.
wix and wordpress are using subdomains.
steem doesn't. so, yes spam on 1 page penalizes how other pages are ranking on search engine results.
. Google's algorithm is very smart and can understand the separations between each username. Now don't get me wrong.
google algorithm is smart and could do it, but actually the domain is what matters. there is no distinction between username. do you have a spare Idea how much computing power they should use to achieve what you say!?
if you post something on your blog it gets high because of steemit.com
if you post some spam google penalizes all the domain not only your @joeyknowsbest folder