Sigh.
What it comes down to is that there are three things that influence the choice
of where to install Trinity, and two are very dependent on the policies
espoused by a given distro:
-Is Trinity being installed through a package manager, or by hand? If the
latter, all bets are off and it could literally end up anywhere.
-Does this distro normally install KDE4 to a segregated location (/opt/kde4,
/usr/kde/4, or whatever), or root it directly in /usr, which results in its
applications landing in /usr/bin, where they can't easily be filtered from the
PATH to avoid conflicts?
-What is this distro's package installation policy? Does it adhere to the FHS
slavishly, consider it useful but non-binding, or ignore it? Are things normally
sent to /usr, to /opt, or somewhere else? Is there a specific reason to violate
the standard policy in Trinity's case?
If I'm not mistaken, there are people from multiple distros (not just Arch
people) now embroiled in this argument, and I don't think it's possible for
us all to ever agree on a "best" installation location. Let each packager make
the decision on the basis of what's best for their distro; multiple packagers
working on the same distro need to hash it out between themselves (ideally
without drawing people from other distros into the mess); non-packagers
can install to /rahrahtrinity if they want to and are willing to deal with the
consequences.