In the current status quo your nightmare scenario (having to debug a codebase with comments in a diffeeent language) is precisely the everyday reality for non-English speaking devs. A Japanese dev could easily make the same comment as you, the difference being he actually has to deal with situation in question on a daily basis.
You could make the argument that English is the "lingua franca" but the phrase itself demonstrates just how ephemeral that is. I've lived in places before where a generation ago Russian was taught as a "lingua franca". Nowadays you would be hard-pressed to find anybody with a good understanding of Russian (good enough to understand technical documentation) there, even amongst ethnic Russians.
The internet has changed what it means to be the Lingua Franca. The ubiquity of English language in the largest internet communities and high quality media content would have to have a very strange reason to change. Before, it was simply a function of your colonizer or trading partners.
You could make the argument that English is the "lingua franca" but the phrase itself demonstrates just how ephemeral that is. I've lived in places before where a generation ago Russian was taught as a "lingua franca". Nowadays you would be hard-pressed to find anybody with a good understanding of Russian (good enough to understand technical documentation) there, even amongst ethnic Russians.