I think that topic was discussed somewhere and maybe i miss it somewhere now, but what i notice for a long time since i use dopus5, is that you can't just press "esc" on keyboard to close system requesters when string gadget is active.
For example, choice any file, press rmb , choice "rename" : window will spawns with one of active strings. So, at this point, pressing on "esc" do nothing at all, and the only way to close that window by "escape" button, its to deactivate active string by pressing somewhere in the requester window. And then "esc" will close it.
From mouse pressing on "abort" works always of course, but close it by "esc" will increase usability a lot.
We can make it as feature request for futher versions (if it not something trivial, like swapping cases in the input checking routine or adding one more case/break somewhere). I see it like "we need adding of the "esc" handle to system requesters, and do the same what happens when we press "Abort" button.