@bitcoinflood 100% wrong. There is a plugin which is quite popular for STEEM users who have Wordpress blogs and want to post content between the two: https://steemit.com/steemdev/@recrypto/wordpress-steem-1-0-1 (there is nothing wrong against posting content in multiple places).

The only downside to publishing on multiple platforms are the SEO ramifications that can come from it, notably Google takes a less favourable view of the same content in multiple places and will derank certain instances accordingly.