The QIF import module allows assigning of placeholder accounts. This is not such a bad idea, as it seems on the first view. But later you open that account to move the transactions to the right subaccounts and get the warning about the write protected account. Then you can remove the placeholder flag, edit the transactions and add the flag again. I believe, at least a warning should pop up in the import druid, if the user assigns a placeholder account as he usually selected the wrong account. To improve the GUI, a dimming of placeholder accounts would be nice - or an option to filter them away.
I think the same error exists in all the other imports as well. (Can't find the duplicate, though.)
On gnucash-de we got the message, also "book closing" is affected: http://lists.gnucash.org/pipermail/gnucash-de/2011-January/007755.html So I move this report to engine.
Changed the account selection in the account tree views to exclude place holder accounts from selection with a warning to that effect which also controls the OK button. The OFX / CSV importers already had a warning dialogue but this was changed to warning message as above to be less disruptive. This will be in version 3.6
