We used RefinedWiki.
On one of the dashboards we have created, we have the following code:

"Welcome to the Finance & Admin Dashboard!"

This code produces a duplicate of the text.

"Welcome to the Finance & Admin Dashboard!"">"Welcome to the Finance & Admin Dashboard!"

I have attached a sample of how this comes out.

Under Confluence v3.5.x this works fine - I am wondering what the new syntax needs to be and also if I can have a coloured / bolded / italic heading in the dashboard still?

I have replicated this issue by placing the offending code into a template and then previewing the template in the template tool. When a page is created from the template, the issue is resolved.