You've kind of touched upon on it but my main argument for not using slang or dialect is most engineering teams are diverse and multicultural (I don't think I've ever worked in or heard of a team where every single developer was from the same continent let alone the same country!).
I'm not saying we shouldn't embrace difference in language in person or over Slack etc but it's just definitely worth bearing in mind that using slang in code comments may act as a blocker for your teammates and potentially slow their velocity.
True. And worth considering of course. I've seen "we shouldn't say this and that" get out of hand and go the wrong way too so, yes, a tempered approach to slang and colloquialisms is a nice balance that still embraces the fun things.
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