I think what they were trying to say was that, if you Claim Access to a Community Copy, then try to add a dollar amount to the box that comes up after clicking (which is set at zero dollars by default), you get a warning notification "error: you must pay at least $15.00". Which makes the idea of hardship buyers tipping less workable - and also prevents claiming the copy the typical way! 
You can still download via clicking the "no thanks" link, which then prompts a second attempt to claim that works. And you can edit the cash box either with typing or by choosing one of the tip buttons lower down on the same window. However the error message appears on attempting to confirm a payment of any type...
Hope this makes sense! I found it out by trying to tip you myself today.
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The Community Copy system was a work around using itch software that was intended for other purposes. I doubt there's another solution except my making the main game free, setting the payment field to automatically fill in a recommended $15, and then letting folks adjust it downward as necessary. But then there are no longer Community Copies and folks might not get that you can pay less or zero?