Non deductible amount always frozen if contribution payment is made online.

The non deductible amount field is always frozen, alongwith the fee and net amount fields when the contribution is completed using an online payment processor. While the latter two require the amount to be frozen, the non-deductible amount should be editable in order to specify an amount which is deductible (total amount - non-deductible = taxable amount) for generating tax receipts. Any particular reason why the field was frozen? Looks like this bit of functionaliyt was carried over since the repo was in SVN.