Steps to reproduce:
1. In a page add a heading text that contains a colon, e.g. "Q: What is this?"
2. Try creating a link to this heading - open Insert Link dialog, Advanced tab and in the Link field type "#Q:Whatisthis?".

Expected behavior is to be able to use the colon character, but it is not possible since it's used to delimit spacekey from pagename of the link.