1) Create a news-item with non-ASCII characters in title (so that Confluence will link to the news with id instead of title)
2) Select the current day from the calendar view to see your post
3) Click "Comments"-link: Confluence claims that page is not found

Confluence will create a link looking like:

http://server/confluence/pages/viewpage.action?pageId=11251?showComments=true#comments

That is, the link contains '?' two times instead of having '&' to separate "pageId" and "showComments" parameters.