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.
[media]
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