I am hearing, more and more, the use of hisself/theirselves. Is this a modernization of our English language - or is it still improper usage as I was taught in school?
It is still considered non-standard English.
That doesn't mean it isn't well established in certain dialects of English.
If you fall into the prescriptive camp, it's wrong, wrong, wrong.
If you fall into the descriptive camp, it's used in specific situations, not randomly as an error.
I'm not a teacher, but I write for a living. Please don't ask me about 2nd conditionals, but I'm a safe bet for what reads well in (American) English.