Note that the rule says:
2.4.1. The language set for a title should reflect the official or officially localized name for that language region.
It does
NOT say official
English localized name.
According to the rule,
Атака титанов would be a valid main title for Attack on Titan since that's the official Russian title. You're not likely to see it often, but it would be totally OK by the rules. It's an official localized title. Totally valid. That's just one of many examples. Same would apply for an official Spanish title, official French title, official German title, official Korean title... I'm pretty sure that is not the intended outcome. This ambiguity is partially what feeds edit wars.
I think there are a few of ways to approach this:
Option A - Declare we're an English-centric site
Staff decide to insert the word "English" into the existing rule. Screw the non-English world. Personally, saying only English localized titles makes as much sense to me as saying only official German localized titles. Why alienate all of the international readers who may not know English? I don't think this option reflects the values of the site, as evidenced by all of the localization efforts the team has put into the site over the years.
Option B - Go purist
Original titles (Romanized) only. The MAL approach. I think this is a bad idea for the same reason many users don't use MAL anymore. It is more defensible than Option A, being fair to all, but a lot of readers would hate it.
I'm one of the people that like to see titles in my own language. However, I acknowledge it is selfish and ethnocentric of me to force my native language preference on others. Whenever I try to evaluate the fairness of a system, I try to put myself in the shoes of the most disadvantaged party. I don't think a Brazilian reader shouldn't have to be forced to have a bunch of titles in English any more than I should be forced to see default titles in Brazilian Portuguese on a Manga site.
Those two options are the low-effort options, involving a simple rule change. The next one would require a bit of work.
Option C - User preference
We have all of the data points in the database that we need. We have country of origin for the work. We (usually) have the title in the matching language. We have titles in various other languages.
There's no need to have the main title field at the top of the edit page anymore. Sites like Kitsu follow this approach with great success.
An example of the priority could be:
1. User preferred language, if it exists
2. Official Country, Romanized, if it exists
3. Official Country, Native Script, if exists
4. Legacy Main Title
What's that Legacy Title thing all about? Well, that's your fallback. Some titles only have the main title. You don't want people making new ones or really using them anymore, but things could break for a lot of titles if you didn't provide a mechanism to display them if they're all that exist. There are a couple of ways to handle that. One way is make them read-only and totally hidden from editor/contributor view. Another imperfect way is create a dummy language called "legacy title" and move it in there, so that editors can remove them over time as part of data cleanup efforts, similar to when we added support for multiple language titles in the first place. I'm just brainstorming here. I'm sure the big brains on the API and UX teams could come up with something better.
I'm not saying the priority order I came up with is perfect. You could argue a different order. Even better, design the user preference system so that they can order them themselves!
If you have a preference system, then users could decide they want to see titles in their own language, romaji, or whatever, and then everyone is happy. Main Title edit wars over.
It would take more work than the first two options, but I think the results would be worth it.
EDIT: Just saw this:
https://forums.mangadex.org/threads/display-manga-titles-in-preferred-language-planned.1107045/
