Hi Alvis Rofhessa, and welcome to CR.
I'll try to answer you're questions:
1. This is basically just to stop people demanding that all their posts be removed on a whim.
In other words, when someone makes a post, they're saying, "yes, I accept that this will go up on the CR public messageboard - it's not a problem".
I was careful to ensure it's restricted to the CR website, though - so we have no right to repost the posts on any other website or media format.
2. This is simply because we've been repeatedly hit by new age prophets, who think it's their god given right to bash other people, sing "hallelujah me!" and generally try and take over the forums - and think we should have no problem with that.
3. This is because proscriptions against posting commercial links have led a few people before to think that because they have a website, and they make no money from it, then it's okay to post the URL 200 times around CR.
It's really just an issue of balance, though - if someon posts a link to somehing the net elsewhere that's relevant to a topic, then it's not a problem - but people who come to CR simply to treat it as an advertising free-for-all may find we aren't impressed.
As in all things, moderation...
Hope that helps, and congrats on actually reading the terms