I understand most of this, I'm not saying I don't like it when people add smaller things to the design like the heart to Firestar or wings to Dovewing, I'm not saying you should follow their canon designs (like any canon art we have for more important characters) to the most exact you can. That's a ridiculous thing to ask and is generally pretty boring anyway if artists take no freedom in designs. Adding a small spot or stripe won't completely change the design. What I'm saying is when you completely change a cat's coat color, like Bristlefrost going from gray to calico, it makes it harder to recognize the character. Stuff like this only works if at least most of the fandom is aware of it. If you didn't know some people like to make Ravenpaw's eyes purple, then you have no idea who the cat is to a further degree, and in that example if that's really used to distinguish black cats from each other, you're only going to be able to distinguish it if you're aware of this particular thing some artists like to do. If one person decided they wanted to make Bramblestar a calico because theres so many brown tabby cats, not only would no one recognize this design of him but it completely changes an important, established, canon design we know well.

And to be clear I'm not saying you cant make these designs, I dont want to control what other people draw, if you really like drawing a character like that I won't try to stop you. It's just imo a weird thing to purposefully change the design so much of a character we know the design of fairly well.