How can steemit be free from spammers and irrelevant posts?

The trick is to limit the number of allowed upvotes per day per person and increase the number based on trust created with time and again decrease it with distrust created with time

The number of allowed posts and comments per day should also be limited per day and per month.

Bring downvotes (though less stringent, and limited in number per day) for comments and posts. We need a bit complicated algorithm. For example, when you are downvoting, you need to specify complete reasoning about the downvote. And the author can provide the rebuttals about the downvote.

The allowed count (i.e. the number of allowed upvotes, downvotes, posts, comments per day and per month) should be tested and should be decided after experimentation.

Amount of credits can be 1 for upvotes, 0.25 deduction from author for getting a downvote with comment specifying why, and 0.5 should be credited for those who downvote.

Should also bring credits for posts that don't have any downvotes and upvotes, but have many page views.

In this manner irrelevant post will be weeded out. And it is required for production of quality content.