Wouldn't it make more sense to, when the user switches languages, check for label/folder name collisions and deal with it then? Alternatively save all the built-in labels (Trash, Bin, etc) as reserved words so users can't create custom folders with those names?

> check for label/folder name collisions and deal with it then?

How?

> Alternatively save all the built-in labels (Trash, Bin, etc) as reserved

So now all localizations are reserved words? And ultimately, this may be a reasonable approach from the beginning, but how many people's accounts are you willing to break to institute this change now?

If there's a collision? Pop an error and offer to rename the custom folder..

This depends on who you want to prioritise.

How many people use Gmail in a language other than US English? How many people change their UI language and rename folders such that there is a clash?

Optimise for where it will have the most impact, and develop a work-around for the minority of users where this causes a problem.

> How many people use Gmail in a language other than US English?

You'd be surprised. There are only about 400 million native English speakers [0], and Gmail has 1.5 billion users [1].

If we assumed that all native English speakers use Gmail, they'd represent not even a third of the users. Of course, there are many non-native English speakers, but I'd assume a significant fraction of them would prefer to use Gmail in their language.

I'd argue i18n has a huge impact, but Google really doesn't optimize for it.

[0]: https://en.wikipedia.org/wiki/English_language [1]: https://www.cnbc.com/2019/10/26/gmail-dominates-consumer-ema...

I think the person you're responding to is agreeing with you that you should optimize for languages other than English rather than for people naming a label "Bin" and then switching to the UK locale.

But how many of those "users" are actually unique?

I, personally, have 3 "GMail" accounts: one @gmail.com, one @ my own domain, and one for work. So if I were the average English-speaking user of GMail, having every English speaker be a user would pretty much cover the 1.5 billion.

(I do not, in any way, think I am the average—I merely seek to point out that it's significantly more complicated to calculate than your post suggests.)

> There are only about 400 million native English speakers [0], and Gmail has 1.5 billion users [1].

Don't assume that only native English speakers (want to) use things in English.

The real question is how many people use advanced searching. I would guess the answer is < 1%.