What Makes a Good Saddle?

As far as width goes, do you want one that’s fairly wide so it stays wedged between your legs?

That will depend on personal preference, and style of riding, but generally no. The seat should be wide enough at the back so that your hip bones are sitting on it comfortably, but if it’s too wide (especially in the middle) it rubs against your thighs as you pedal and gets uncomfortable fast!

Generally when you’re riding, you want as much weight on the seat as possible (obviously this rule varies based on terrain). In this effect, your body weight on the seat is going to be MORE than enough to keep that seat between your legs. When you do need to stand up (hops, bumps, power), a wide seat would get in the way.

I agree with the first part, but disagree with the 2nd part; I think the Velo seat base and it variants (K1, KH, Impact) is too narrow AND too flat, plus the curve is wrong positioned in relation to the seatpost location. This makes you still sit too much front, even if you put up the nose.
The rubbing is not the issue, it’s sharper edges and less friendly contact. I much better like the Semcycle seat which is wider and higher, not just only for the sitting-comfort but even for the riding; due the lack of contact with the unicycle I have “trouble” with exactly estimating the direction of the wheel, since I now cannot tell it anymore sitting on a flat seatbase with hardly any decent suspension (which also causes each bump to hit my spinal cord harder then one with a little more cushion in stead of foam).

I ride about 600 to 700 hours a year, all of it with a back pack of several kgs that also has to be supported by my heavily loaded seat-bones.

I add a swappable strip of sheep skin. I select the sort of skin that is used in hospital bedding. Attachment via a handful of lacky bands. It is remarkably successful though I will still not ride the full 17km to work without hopping off for a brief adjustment of the crown jewels two or three or four times.