The ironic usage makes for compelling dialogue and comports with stereotypes about Southerners as formal/restrained. So that's what ends up on television. At least that is how I think I came about having that impression.

Yeah, I get this a lot, especially from non-southern in-laws who think it's a hoot that they've "cracked the code" and can "speak southern". Being repeatedpy stereotyped to your face gets old pretty quick.

For folks who don't know, here's the best explanation I can offer from growing up in the Atlanta area (but well outside the perimeter):

"Bless your heart" is most commonly an expression of sympathy.

Sometimes, it's sympathetic towards the hardship someone's going through (e.g. "and right after his grandma passed, bless his heart.")

Sometimes it's sympathetic to the trouble someone went through (e.g. "oh bless your heart, you didn't have to go out of your way to bring extra! Thank you so much!")

And yes, sometimes it's an expression of sympathy for the fact that life must be hard for you because of your ignorance, stubbornness, stupidity, or arrogance (or some other such stunting quality) (e.g. "and he thinks he can graduate from Tech with those grades, bless his heart," or "bless his heart, I just don't think he's ever had anyone tell him no in his entire life.")

Yeah, it's a pretty versatile phrase that's hard to explain. But it does often have a connotation of childishness or naivety, even when used sincerely.

It is often used an expression of thanks or appreciation, but I associate that more with an elder speaking to someone younger.

Most of the time, it is an genuine expression of true empathy, but it's not uncommon to be used as a passive aggressive expression of false empathy. It's that childish connotation that give it the extra bite when used passive aggressively.

And that plausible deniability, where the phrase is used in a genuine context often enough that sometimes you can't tell that someone is throwing shade, is very much a reflection of southern culture.

Source: Grew up in Georgia and North Carolina, with some family in Alabama.

You mean kinds like "I wish them well" here?

My comment is an internet comment about idioms, not a comprehensive linguistic treatise.

You seem like you're looking for something to be upset about. I wish you well.