Let me start by saying that this question is not a criticism of any one community or their dialect. I'm asking this question from the mindset of there being possible religious obligations to use the most "correct" Hebrew possible.
Sephardim, Ashkenazim, etc. when we follow the evolution of Hebrew in each community, we see that the language evolved and adjusted to the norms of each location/situation.
A quote from an article on Chabad:
This being just one example.
All of these linguistic traditions evolved from the exile. When we lost Israel and didn't have a centralized location to keep the "norms" (so to speak) of things like language intact, they evolved in each of the four corners of the world.
My question is this:
If modern evidence comes along that shows the way some or all of the communities changed the pronunciations are considered historically inaccurate, do we have a divine obligation to change our behavior to most reflect the historical language norms?
The reason I ask is if the language is divine and given to us from Hashem, wouldn't those pronunciations be just as important as the words themselves?
Could there also be Messianic implications in relation to "Pure Speech" ?
For then I will make the peoples pure of speech, So that they all invoke the LORD by name And serve Him with one accord. -Zephaniah 3:9