It seems that you may not fully understand how these "platforms" work.

Most of the platforms are dapps or front-ends and not stand-alone platforms. YouTube or soundcloud are completely separate, for example. But, spanish-tribe is a front-end, steempeak is a front-end, Dtube is a front end, 3speak is a front-end and even steemit (the first one) is a front-end. If you post something on one of them, the post will appear on the steem blockchain. For some of them, you need specific tags for them to appear (such as #spanish for spanish-tribe or #photography for photostreem). But they are all on the steem blockchain. Some of the video and audio platforms post automatically to the steem blockchain when you upload a video or a song/track onto their platform. I think 3speak does this, but I'm not sure about DTube, DSound or all the other ones. So if you post a video on 3speak or Dtube, it will appear in your blockchain feed even if I'm looking at it on steempeak or steemit.

So why am I trying to tell you all this? What is going to happen is, curators will eventually notice your multiple posts, stop voting for you, as well as tell other curators what you are doing. You also run a big risk of being reported to the steemcleaners and getting downvoted (or even worse blacklisted), which is why it's good that you responded to my comment! I'd really hate to see you downvoted just because you are unaware of the way steem works.

Posting the same content twice, makes you look like you are trying to get rewards twice for identical content. I would sure like to know who the users are who told you this is ok?