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Farmer ordered to pay after judge says thumbs-up emoji amounts to contract acceptance

https://www.theglobeandmail.com/canada/article-farmer-ordered-to-pay-after-judge-says-thumbs-up-emoji-amounts-to/

Judge rules Saskatchewan farmer’s use of thumbs-up emoji was contractual agreement

Farmer ordered to pay after judge says thumbs-up emoji amounts to contract acceptance

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In many US states, even a verbal contract is legally binding. Obviously this depends on many factors, the terms have to be reasonable and it has to be clearly communicated (and it's generally harder to prove a verbal contract in court). Text and email communications are the same way.

In your example, it likely wouldn't be considered a valid contract though. The terms have to be reasonable for both parties and there has to be a clear understanding that it is an agreement. Getting "ok" back is presumably sarcastic or not genuine.