Thanks, these are great ideas. I never thought of doing this way.

The site dos not take in user generated content that is immediately displayed. The data is first curated and verified so the attack will be a bit harder. So there is fresh (delayed) content constantly.

That is exactly the reason of the captcha: to give a person something to do that wastes a bit of their time and that is familiar to them.

Yes, in other sites I have used captchas to prevent automated abuse.