I ran into "The payment was remitted" at work, and I wasn't sure initially if they said they were denying to reimburse me, or if it the payment had been sent out.

Weirdly, the verb "to doubt" used to be used in the opposite sense to how it is now. So, for instance, if you say "I doubt it's going to rain", that means you think it won't rain. But a few hundred years ago, it would have meant you think it is going to rain. (And of course if you lived in England, you'd probably have been right.)

If you've read Gibbon's The Decline and the Fall of the Roman Empire you will have wondered at the meaning of both sensible and insensible which both seem to alternate between opposites randomly throughout the book.

If we take archaic usage into account, there are many more words that now mean the opposite of what they used to mean, e.g. “awesome”.

When was awesome used to mean bad?

One of the OED meanings is still "appalling, dreadful, weird". I've seen usage meaning the same as "terrifying" in older texts but I can't find an example just now.

they mean that since _everything_ is awesome these days, awesome now means "ordinary"

I didn't meant that at all.

Do you mean “awful”?

No, I meant "awesome" but "awful" is an even better example.

"awful" in this context reminds me of this famous story about Charles II (https://quoteinvestigator.com/2012/10/31/st-pauls-cathedral/)

From the article:

"When the excursion was complete the monarch told Wren that the new building was amusing, awful, and artificial. Remarkably, Wren did not feel insulted; instead, he was greatly pleased."

these are called "Janus words" or self-antonyms. Such as "flammable" and "inflammable".

https://en.wikipedia.org/wiki/Auto-antonym

Buckle — to collapse, or to fasten

Raze/Raise might be a “phonetic contranym”

im wondering how an AI would deal with this sort of thing. would contronym strings, be like forbidden ASCII?

Inflammable?

That's a dangerous one. The builder asks, is this insulation inflammable?

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