[maemo-users] My N900 has diffmo as an essential package; safe to remove?

[From: Paul Hartman]

Hi Maemo users,

I wanted to install diffutils-gnu on my N900, but it seems to conflict
with diffmo, and diffmo seems to be "essential". I'm not a Debian guy
and am not entirely familiar with how the apt-stuff works and why this
package is essential. As far as I can tell, no other (installed)
packages depend on it, but I may not be looking it up properly. I
don't remember installing it but it's entirely possible that I did one
day and just don't remember.

So I suppose I have two questions:
1) What causes a package to become "essential"?
2) Is it actually safe to remove diffmo? I don't want an unbootable
device or anything bad like that.

Thanks.

Some apt-output is below:

Nokia-N900:~# apt-get -s install diffutils-gnu
Reading package lists... Done
Building dependency tree
Reading state information... Done
The following packages will be REMOVED:
  diffmo
The following NEW packages will be installed:
  diffutils-gnu
WARNING: The following essential packages will be removed.
This should NOT be done unless you know exactly what you are doing!
  diffmo
0 upgraded, 1 newly installed, 1 to remove and 2 not upgraded.
Remv diffmo [1:2.8.1-21]
Inst diffutils-gnu (1:2.8.1-18maemo3 Extras:2.0/fremantle-1.3,
Extras-devel:2.0/fremantle, Extras-testing:2.0/fremantle)
Conf diffutils-gnu (1:2.8.1-18maemo3 Extras:2.0/fremantle-1.3,
Extras-devel:2.0/fremantle, Extras-testing:2.0/fremantle)

Nokia-N900:~# apt-cache rdepends diffmo
diffmo
Reverse Depends:
  colordiffmo
  diffutils-gnu

Nokia-N900:~# apt-get remove colordiffmo diffutils-gnu
Reading package lists... Done
Building dependency tree
Reading state information... Done
Package colordiffmo is not installed, so not removed
Package diffutils-gnu is not installed, so not removed
0 upgraded, 0 newly installed, 0 to remove and 2 not upgraded.