A language list is usually a marketing line. Here it is a constraint that shaped the product, and the interesting part is not the list but what it rules out.
The filter nobody mentions
An English-only marketplace does not politely ask its sellers to speak English. It selects for them.
A person who makes something well, prices it well and knows their trade completely — and reads Marathi rather than English — is not a worse seller. In an English-only product they are simply absent, and their absence looks like nothing. There is no error message for the seller who never signed up.
That is the quiet filter: it does not reduce quality, it reduces who is allowed to supply it. And it filters hardest exactly where the goods are most interesting, because the person three generations into a craft is not reliably the person comfortable in a second language.
What it forces on the screens
No text in images. An image with words baked into it is an image that exists in one language. Everything readable has to be real text.
Room for the sentence to grow. The same sentence is a different length in each language, sometimes by half again. Any layout that only works at English's length is broken in eleven other places, and you will not see it unless you look.
No clever sentence construction. Assembling a sentence from fragments — a noun here, a verb ending there — works in one language and produces nonsense in the next. The whole sentence has to be the unit, which means more lines to maintain and fewer tricks available.
Errors in the list too. The sentences written furthest from the reader are the ones that matter most when they appear. A refusal from the server is as much a part of the product as a button, and it has to be translatable or the constraint is a pretence.
What it costs, honestly
Every new screen is eleven more translations. That is a real brake on shipping, and it is the reason to keep the text on a screen short — not elegance, arithmetic.
A stale translation is worse than none, because it is confidently wrong in a language the people who wrote the feature cannot read. Growing the list is cheap; keeping it correct is not, which is the argument against adding more.
Some things are better left alone. A host is a host. Translating a word nobody uses in translation helps nobody.
Why it is still right
The app is written in eleven Indian languages besides English, and that decision is not generosity. A marketplace's quality is the quality of its sellers, and anything that narrows who can sell narrows the goods.
Making the product work in somebody's own language is not a service offered to them. It is the condition of them being here at all.
Questions people ask
Why not just use automatic translation?
Because a mistranslated deadline or fee is a person losing money, and nobody here could read the mistake to catch it.
Does the whole product work in every one of them?
The app does. The staff console does not, and will not — it is an internal tool used by people who work here.
Will more languages be added?
Possibly, but the cost is upkeep rather than the initial work. Twelve kept correct is worth more than twenty kept roughly.
More: how Metzee works in twelve languages, language and your buyers, using Metzee in your language, eleven languages.