To demonstrate this issue, here's the page title for the Add Comment page for MC-200000:
Add Comment: {0}: MC-200000 - Jira
The extra characters "{0}:" are almost certainly incorrect, but I'm not entirely sure what the title is intended to look like.
Not sure how this can be fixed since even Atlassian's own Jira for fixing Jira bugs has this "issue". https://jira.atlassian.com/secure/AddComment!default.jspa?id=246974