you’re right, sorry! the field, you have described is html allowed.
but this entry, you have named, has no effect to the behavior of opening events from the calendar – or did i understand something totally wrong???
anything i enter here, has no effect.
the way of opening changes, if i modify the entry at:
events -> settings -> general -> all calendar options -> event title format (my own translation, unfortunately no chance to upload a picture here)
…at this point no html is allowed, bt it has effect to the entry in the calendar.