I recognise some of the orphaned packages after a fresh Trisquel install as
stuff Ubiquity uses from looking at its source for a bug in 6.0. So I guess
i might be stuff it doesn't self remove just in case. Whatever, an apt-get
autoremove of them has never given me any problems.
The Update Manager upgrade process last time I used it was again the same as
Ubuntu's with modifications to the package lists and deleted all the cruft
and orphan packages. I haven't tested the 6.0.1 -> 7.0 upgrade yet, but I
don't imagine it'll be any different once bedded in.
apt-get autoremove is to my observations as legimet and the man page says.
However, having used first Debian then Ubuntu then Trisquel since around 2001
I have seen something like the situation jxself mentions from using both
aptitude and apt-get. I don't know whether it's something like and aptitude
install followed by an apt-get remove doesn't remove the additional suggests
installs or not for certain, but that's what I thought at the time.