Omfg...bacon grease popcorn...I'm about to take 10 years off my life

Popcorn made in pre-used oil can be awesome, and an easy way to get rid of 100ml or so.

Then there was that time in college I tried to re-use oil I had previously fried shrimp in.

Turns out shrimp-flavored popcorn is not an enjoyable experience!

But singapore site links USDA q&a on how to reuse it safely and has section for "what you need to do if you reuse oil". They don't particularly advice or encourage single use.

Oil quality is dependent on storage method (strain it with filter, keep airtight non-transparent container etc) and cooking temperature so people need to be informed, but I don't see reusing it once or twice with appropriate care cause significant harm.

That's if you take it beyond the smoke point. Which you wouldn't do if you are trying to avoid free radicals in your food to begin with. Even vegetable oil is extracted through a heating process.