There are several JIRA tickets that we have where a person is being instructed to update database fields, where the value of the field is a URL. However, as soon as JIRA sees http, it interprets the rest of the line, until it reaches a whitespace character, as part of the URL - turning it into a link and URL encoding it. This is a problem because, being the literal value of a database field update, it is terminated with a single quote, which in turn is being (wrongly) encoded as '.
Example: update field1 set value='http://some.url.com/some/path/to/file.html'
EDIT: the above example looks fine here, but if I do the same thing in a JIRA comment or ticket description, it will come out looking like update field1 set value='http://some.url.com/some/path/to/file.html'.