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I know this question will raise eyebrows and I kind of enjoy it.
I passed the interview with a company making software, and got an offer. May I ask for a sample of their codebase? The reason is that the company is founded and run by a number of highly talented PhDs in Mathematics and Physics, and this often implies the quality of the source code is pure junk (to quote a classic: https://academia.stackexchange.com/questions/17781/why-do-many-talented-scientists-write-horrible-software). Every "pure" software engineer knows that: behind a brilliant researcher an awful programmer is hidden, and I don't want to be the janitor cleaning after him/her.
Is that an acceptable request? If so, how can I motivate it without sounding rude?