Jira uses to manage the comments come from Outlook the following way:
- it automatically collects all images to the issue attachments
- it replaces the image with the [cid:] reference in the comment
That's why you can see something like that in the comment:
If you would like to avoid such attachment references to be created in the comments, tick the Turn on filtering of [cid:] messages from comments checkbox in Jira Administration > HelpDesk > Access: