I think that's especially silly, since (almost) everyone uses some combination of these two. Particularly in the rest of the Anglosphere each country's norm will have elements of both British and American conventions. Even in the UK and US different publications will have standards specifying the use of one or another spelling for "ise/ize" or "practice/practise" and things like that. It would be weird to mix dialect like "garbage can" and "dustbin" but spelling is absolutely fine (as long as you're consistent with each choice).