[episteme]

Your rule is describing this Friday, not next Friday.

[tromp]

Except on Friday's, when "this Friday" means today. On other days, many people indeed use "this" and "next" synonymously.

[hawkice]

Perhaps this is regional? I would identify this Friday as the 15th, and next Friday as the 22nd. Next Friday always means the Friday after the next one, which I notice is insane as a matter of logic, but is the local usage I am familiar with.

[tromp]

> Next Friday always means the Friday after the next one

You're using "the next one" i.e. the next Friday, to refer to the first one after today.

[hawkice]

Yes, next Friday is not the next Friday, those two phrases are very different despite that being weird.

Not endorsing this, just reporting from usage.