Two other things that come to mind:
- If your browser supports auto translation or has an extension that does translation, it might be trying to translate the English into Greek if your native platform language is Greek.
- There may be some weird situation where your browser's default sans-serif font is a Greek Alphabet font. Specifically, in the blocks editor it looks like the text is a direct character-for-character substitution from the Latin alphabet to the Greek alphabet, e.g., when => ɷηεν (omega, eta, epsilon, nu). I'm not sure exactly where you would set this, but check your browser and operating system settings. You may temporarily want to try another browser to see if you get the same issue to eliminate that as a possibility.