No! You should not. You should rebel against this ridiculous imposition. You've really been welcomed to the world of Medium now. I too, had this problem, and I now leave a little note to tell them it's written in British English and I'd prefer no edits please. Let me guess... Illumination? Here's my recent rant on the subject https://medium.com/fuck-niches/fuck-off-grammarly-f492cbb68f8c