The standard directory for temporary files is /tmp, which is not really handy for people who use tmpfs for /tmp (and I guess there are plenty of Gentooers that have this). I think it would be an enhancement to use ~/.fidelio/ (or anything that's likely to be less volatile than /tmp).
Err... You can do whatever you want for /tmp. If you're chosing to make /tmp tmpfs then you're causing an issue. However, if Fidelio is forcing /tmp you should file a request upstream to change the behavior. In either case, this isn't a Gentoo issue/bug.
