I think valuable / invaluable actually have different meanings. Something which is invaluable, is so important a value should not be assigned.

That's called a contronym, which (as you said) is different than what OP is looking for

https://en.wikipedia.org/wiki/Contronym

Caregiver/caretaker is a fun one I had never considered.

I don't think either were ever said by competently literate people (wtf is "irregardless"? And do they mean they could "care less" about a subject or do they mean the opposite but don't understand negation?) so idk if this fits what OP was saying entirely. They're just obvious mistakes that have been normalized as people got dumber, right?

I find intensifying to be more natural than negating for things like “I couldn’t care less,” or “irregardless,” or “misunderestimate” to a certain extent — if something is “worthwhile regardless,” I don’t have to regard that, but if it is “worthwhile irregardless,” I really don’t have to think about it at all. It just seems right that if I put a bunch of negative words in one sentence, it should be really, really negative, instead of it being negative if I used an odd number and positive if I used an even number; same with prefixes and suffixes. I think it’s probably too much to try to reform English to work as such, but if I were building a conlang it’s what I would do.

I could care less

Hi Dr.Nick!

"Are you down for that?" "Yeah, I'm up"

Similarly, peel and unpeel.

One of those also means to add a bone to something. Coincidentally, that's why I got fired from my job at the butcher shop.

..are opposites

My pedestrian is half run over.

It means authorized decision. The decision can be a punishment.

I often thought awful was an odd word. Surely awful = full of awe, but it is frequently used to describe things that have little to no awe.

Also I have now said the word awe too much and it looks strange.

As a non-native English speaker, I always have to think a second extra about "terrific", about it being negative or positive. Probably because it sound similar to "terrible".

What a country!

"I'm garnishing my bank account with your wages."

Your lease/rent example both have the same meaning.

And the "literal" issue is in the last 20 years from maroons using it incorrectly.

You say "literally" to me and I'm taking you at your word.

Within a region, does table ever mean both of those?

In the US, it means to set aside or ignore it, but never means to continue the discussion. In the UK it means to discuss it, does it ever mean to also set it aside?

Literally literally means figuratively, or literally, however figuratively literally only means figuratively.

Really, it's a way to spot a bad dictionary.

I think the word 'unironically' has started to fill the void left behind after the word 'literally' was changed to mean 'figuratively'

And it's been like that for decades! I only learned this recently. https://en.wikipedia.org/wiki/Literally

not really; "it's all downhill from here" means that the hardest part is behind you, and progress will be easier from here

No that's different. A contronym is where the same single word has two opposing meaning. OP is asking for two separate words that sounds like they should be opposites but actually have the same meaning, like flammable and inflammable which both mean "can catch on fire".

Good example! And what's with "fast food" anyway? That's not how fasting works

Egregious is distinguished only on a negative sense

It sounds like it should mean something flame-proof. Like destructible - indestructible.