There is no indication when read messages in the drafts folder are hidden. There is no icon for this state and so it is easy to think the hidden drafts just don't exist. Probably the best solution is not to allow this setting on a drafts folder at all. Almost by definition, these messages have been seen. But if the setting is allowed then there should be an icon that indicates it.
Though adding icons is probably easier to implement, I agree with the idea that hiding read messages has not much sense in draft folders. Accordingly, the related options "Hide read threads" and "Hide deleted messages" should also be disabled.
Created attachment 1688 [details] fix candidate As commented before, it disables hide related options on draft folders, rendering hrm icons unnecessary.
Fixed in http://git.claws-mail.org/?p=claws.git;a=commit;h=9470e632a121897af943b4c2972a7f1dfe8a0673