Comment 84 for bug 209695

The fact that an advanced user can workaround the problem by tweaking variables in a configuration editor does not make the usability issue vanish. Moreover, setting a variable named "deleteTempFileOnExit" to F, according to its name, will leave unwanted files on the disk: not quite what we (I guess) want.
By the way, it's also true that the fact that this is actually a bug is debatable, as it reflects the intended (mis)behaviour.

So many thanks for the useful workaround, but to to me, this issue is still an issue.