Was this sentence written by a Non English native speaker?

I have a friend who claims to be English, and he sometimes makes lots of spelling mistakes due to his dyslexia and dysgraphia.
So his sentences sound sometimes illogical or "disjointed", but with a little effort I can always understand what he says.

That's what he wrote :
"This is not a personal attack on the anonymous group..... but the next time you put your mask on. Remember that when you wear it? You wear this sigil. I know who this sigil belongs to" (He has edited the post, he had formerly written "where" instead of "wear".
And there was an attachment of a picture of an Anoymous mask and the sigil of Satan. He basically meant the mask is a sort of subliminal message (I know, total conspiracy theorist)

So, a friend thinks that it's crystal clear this was written by a non native speaker, while I think there's no reason suggesting he's non English(or anglophone in general):

1)His semantic choice is very good. Not many non native speakers (unless they are very fluent) would have come up with the terms "sigil" or "attack ON".

2) Native speakers(more so if they are dyslexic) make spelling mistakes more frequently. Again, I am a non native speaker and I never confused "they're" or "their" while sometimes even the most educated native speakers slip. It's just because we don't think about the pronunciation of the words when we write, while you do.

3) The intonation of the sentence. I agree it sounds illogical, no cohesion and disjointed. It lacks coherence. But if you read "Remember that when you wear it?" with intonation it's something that you would say in spoken English, that exact intonation, even though grammarly it doesn't require any question mark, as it's not even a question. But in spoken English you might change intonation(Also, tell me if this phenomen has a name in English). At least in my language we wouldn't have that intonation.

4) "Wear" and "where" have about the same pronuncation in British English, it would make more sense for a Brit to get them confused.

5) Mispellings and disjointed English is common even among Natives(unfortunately). That doesn't make them less English, American or Australian. I am a non native and this happens frequently. I read what some people says and I am like "WTF?" Although, you can still tell they're Native speaker by their lexical choice and by their general use of the language.

Don't get me wrong, I am not saying this guy sounds particularly "English", but I also can't see the ultimate proof he isn't., that's why I decided to ask for the opinion of Native speakers