Is the Transfer Fee stored in an address's root node alterable or will it be permanent once set?
We originally had planned a way to lock the transfer fee for a particular amount of time and require you to announce a higher transfer fee in the ledger. The whole scheme got unreasonably complex, and we ditched it. We hope gateways will contractually obligate themselves not to raise the transfer fee without sufficient advanced warning. No transfer fee applies when a balance is returned to its issuers and issuers must accept their own balances at face value. So you can't really raise your own transfer fee as a way to make your debts worthless. (You'll just make them less desirable, likely causing people to stop letting you hold their money.)
What was the case against not letting them alter it at all once set? As in, if they want to start issuing new debts with a new fee they can create a new address. My issue is that the cost of transferring the debt would be a key ingredient in how I value it. One of the better things I'm seeing in Ripple is that it would give debt issuers
less control over the transference of their debt, and less ability to suddenly make arbitrary rules or fees about how that happens. Fees would be set up front. They can charge a fee, perhaps they can even decrease it, but I don't see why you would allow them increase it. Particularly as you (being Ripple) ultimately want people to keep their IOUs in the system rather than cash them out.