I cannot edit sold or unsold. This sucks! I don't like it.
As we learn and improve our editing skills, we should groom our images periodically so as to improve chances for better sales. If this indeed is a DT change, then I find it to be counterproductive and, IMNSHO, I think it will hurt sales.
And there is another thing to think about ... there are many instances of words in titles that are not spelled correctly and that should be fixed. For some of us, that is not now possible.
If this is a glitch in DT site, that is one thing ... if it is an unannounced change, I find it unprofessional not to inform us in advance.
Since, in the past, DT has gone out of their way to courteously inform its contributors of upcoming changes, I tend to think this might be some kind of glitch.
My guess is that a flag is being applied to the title text field that shouldn't be. I notice that for my images, only the newest uploads can have their titles changed. The ones that are a bit older (online for more than a couple of weeks) have a non-editable title text field.
I can't change any titles, sold or unsold. I don't like this because the title does play a role in searches, and losing control of that variable is not good. Just as we tweak keywords long after an image has been online, it's nice to be able to tweak the title for better visibility. My two cents...