But it got me wondering about conditions with multiple instances such as: "if (true) { if (!true) { return } ... }"
Is arrow code sometimes unavoidable? Or should I be setting flags for everything?
The important thing is clarity of code. If arrow code makes that part of the code easier to understand and less likely to lead a future dev (who may be you!) to make a mistake, then it's a good thing.
If setting flags makes that code easier to understand and less likely to lead a future dev to make a mistake, then that's a good thing.
It all depends on the project, and has to be balanced with a consistent approach also being a good thing. If flags are used everywhere else, then use them even if arrow code would be more clear for a given section, and vice versa. This is the purpose for "house rules" about coding style, and such house rules are usually the best way to go.
My TL;DR is: anytime someone says that "X is always good" or "X is always bad", that person is wrong. X may usually be good or bad, but there are always exceptions.
I mean, sure, nobody should be using it for loops, but if you're jumping right to the end of a function (or a while loop) and doing cleanup operations, is that such a bad thing?