Google’s John Mueller answered a question around how Cyrillic script and those special characters and/or accent marks on characters, impacts your rankings in Google. The short answer, at least on how I understand it from John, is that the impact is minimal at most.
He said that in the case he looked at it, with French and German, it “is not the case” where there is an impact on rankings.
John said you should write content the way the content should be written, the way your readers can understand it. So don’t not use Cyrillic when you are suppose to use it and the same goes the other way.
John Mueller said you should “essentially rank for both of these variations” if done right.
John said this at the 40:46 mark into the video. Here is the embed:
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Here is the transcript:

The whole SEO community in Romania thinks that by writing without the Cyrillic and special characters you can rank better.
Mihal says no. So some of the SEO community in Romania thinks this apparently.
The top argument that people use is that people search without the Cyrillics, so we should write without the Cyrillics and we’d rank better. Is this true?
How does Google handle this in German and French? What is your take on this?
So I don’t really know what is unique with the Romanian search results, if that is something that where you do see this kind of difference.
In general, in German and French where I looked into this a little bit, this is not the case.
Some people do search without the special characters and a lot of people search with them. And it is something where if you create your content to actually be readable, it will essentially rank for both of these variations.
It is not the case that the search results are exactly the same. Because sometimes people mean subtly different things, espesially if you are looking at French for example, sometimes having an accent or not makes a difference in the word that is actually used. That is something where it would be normally to see subtly different search results.
But I wouldn’t see that as saying I should be writing in a way that is essentially not correct for your local language. Especially when users come to your pages and read your content, and it looks like you are really not writing in their language – that is something they are really not going to appreciate. I assume for at least most cases.
So with that in mind, my recommendation is to be to write normally, write the content in the language properly and that is something that we should be able to pick up accordingly in the search results.
If you see situations where we are really ranking things wrong when people commonly search in a variation of a word that should be showing some pages and isn’t showing them at all. Then feel free to let me know, send me some example queries, some example pages, where you are seeing this happening. And I can pass that along to the search quality team where they can take a look at that specifically.

Forum discussion at YouTube.
This post was scheduled to go live today but was written earlier – I am currently offline today.