Donations are completely optional. Anyone can leave a comment, a tip or a donation is just extra appreciated. Comments will be displayed in order of donation amount though. All comments will be displayed immediately but will not be placed in their appropriate order until at least 3 verifications have been received.
All fields are optional. Your comment or donation will just be marked as 'Anonymous' if you don't provide a name. Comments can be up to 250 characters. No html allowed but you can put a url in if you like. It will not be linked at this time. The reason for the amount selection is just to provide a quick link or qr code on the next page. You can obviously send any amount you would like. We're using the blockchain.info receive payments api though so a minimum of 0.0005 BTC is set by them.
I personally reserve the right to remove any comment that is inappropriate. I won't generally censor anything... just don't post urls for CP or anything like that.
Donation amount exchange rates are provided by the blockchain.info exchange rates api