You point out the real pain point when it comes to downvotes. They use up your power and you do not earn curation. Like you said you missed out on 10sp...
Sure there are the long term incentives (what untimatly got you to flag in the first place) at play with downvotes but those incentives are far removed from the immediate incentives of curation rewards.
There must be a solution here. Curation rewards for flags? How would that work? No power for flags, that has problems. 3 free flags a day? That has its own misaligned incentives. I am not sure.
Thanks for the response!
Cheers