Configuring preferences and options in Outlook.com
My wife and I are having the same problem. The only wrinkle is that only my wife receives the Icelandic message when I post a new calendar entry If she posts a calendar entry, the notification message I get is normal. Since the calendar itself shows the calendar entry properly this is not a big deal but just curious. The shared calendar happens to be my personal calendar. We have been on Outlook.com for years and this has only started recently. I would guess that it started somewhere after the recent major upgrades to Outlook.com.