I've set up my Office 365 account to use English as display language, while my co-workers are using Norwegian as their display language. So menus and so forth on our Sharepoint online sites are for me displayed in English, while my co-workers get the same menus in Norwegian.
I've create a few, modern communication sites, in which the default title was set to "Communication site", and locale set to Norwegian. When my co-workers who are using Norwegian as display language, set a new title, the new title does not affect me - I still get the default "Communication site" title.
So it seems that when we create and customize new sites and their titles, the page's title will be different depending on the visiting user's default display language - users like myself who use English as display language, won't get the correct page title, while users with Norwegian display language get the correct title.
How does other companies handle this sort of issue? The way it works now, it seems we have no control over what page's title will be displayed to our users, as this seems to be totally depending on whatever display language setting they've defined.