Yes it is pretty well known fact among coticule users that the diamond s fracture the garnets and lead to faster cutting but a more damaged edge.
Pieter, I am not saying you can't shave off every coticule and I am not saying the shaves you can achieve are not comfortable. I am saying picking a coticule at random and expecting 10k plus edge is unreasonable because most top out much lower than that. Very fine finishers do exist but are most people going to put the time and money in to find one? No they will stick with what they've got and shave off it even if it is not the best that edge could be. How are they to know any different if they have only tried a few coticules, they might think its the best thing since sliced bread and that my friend is the common goal to find a stone that you are truly happy with. A very comfortable forgiving edge is easily obtained with a coticule but that sharpness is not what a high grit synthetic can provide and the edge resistance can mostly be felt. This is why such tricks like unicot were invented. To bypass the keenness limit of mediocre coticules. It can be used with any coticule but helps those that max out keenness lower then ideal.
I have shaved of coticule and had a mediocre shave and off another the best shave in the world. The point I am trying to get through to new guys is not every coticule is an ideal razor finishing stone.
Do you know how many times I get messged or even in posts where members struggle to get that final edge. The first thing we tell them is to use a misty slurry and more half laps, strop it etc. The whole point is the coticule is struggling to finish the edge so if you are coming to the finishing stage and water only laps aren't doing it.. There's a problem and that can be dissected as well doing a one stone honing. Of course it works but is a lot harder then using up to ~5k and synthetics and using water only the coticule. Slurry creates damage to the edge. Water only laps should be used for finishing for the best possible edge. I even think Dr Matt would agree with me on that one.
What I don't like is guys being misinformed. Coticules are wonderful stones I have spent hundreds of hours learning and this is my experience with them. Not all are razor finishers... Simply put. Are all jnats finishers? No why on earth would all coticules be. They are natural and vary and that's what makes them so intriguing. The search for that magical edge only given when a certain ritual is used. So go and have fun and you will figure out what works and what doesn't. Just don't beat yourself up if you've tried everything and nothing is working. You got a sub par coticule. They are more prevalent then most dedicated users would like to believe.
Food for thought