The Voluntary Donation Amount field should not be displaying on the Participant Pledge Entry form within a Participant HQ.  If this has been reported, or you have seen this field enabled on the form, please do the following to remove it:

1. Go to Communities > Special Events > Friends Asking Friends > Kintera Thon
2. Hover over your event and click Website Info
3. Click Customize Forms
4. Click Select next to Participant Pledge Entry
5. Click the Save & Preview button
6. Click Confirm
7. Go back to the Webinfo Checklist and click Update Your Event Now

If this does not resolve the issue, please click Create Case and provide the event name that this field appears in and an analyst will follow up with you.