How “Not Canon Compliant” is too not canon compliant for you?

Obviously I know this is the Dramione sub so we’re pretty non-canon compliant already but we knew that

I’m just curious as to where everyone’s limits are when authors deviate from canon as I noticed some fics aren’t getting as many hits/kudos when they do.

Edit: Wow. I didn’t expect the amount of people commenting on Muggle AUs. I wasn’t thinking of that when I made this post. I was sorta thinking along the lines of character identity or personality but still in the Magical world