Most site's pages link to their home page. I do not see how only that would get somebody banned.
I am sure it helps send your visitors to the home page, but I doubt it helps
SEO very much.
I have heard that subdomains - subdomain.domain.com - are considered different domains in some ways, maybe something of use there. But if all you had to do was link to your site from your own subdomains everybody would already be doing it.