In Russian ë is a completely separate letter pronounced "yo". This is non-intuitive to English speakers, which is why the name in question is almost always anglicized as Pyotr, not "Pëtr".
> It's really weird seeing letter ё in English language title.
It’s not, for the varied reasons I gave. I know that this is yet another variant. I agree there is a problem with it in that its meaning is not well-known (so you may want to use more well-known alternatives), but not that the diacritic itself is “weird” or foreign to English language users.
