Without digging into exactly what character decoding/encoding is occurring here, you can reproduce the issue with this set of steps:

On Windows 8, put any Emoji into an email message with the Outlook web access client (https://outlook.office365.com/). Copy the character from your message into the system clipboard (select, ctrl c). Paste the emoji character into a Jira field. Save.

Results in trace:

Error creating issue: org.ofbiz.core.entity.GenericEntityException: while inserting: [GenericEntity:Issue][summary,test][watches,0][creator,twilder][created,2015-06-29 11:37:18.528][timespent,null][timeoriginalestimate,null][project,10105][description,😣][reporter,twilder][type,10001][priority,3][number,2760][environment,null][security,null][timeestimate,null][duedate,null][resolutiondate,null][votes,0][assignee,null][id,17121][updated,2015-06-29 11:37:18.528][workflowId,19521][status,10200] (SQL Exception while executing the following:INSERT INTO jiraissue (ID, pkey, issuenum, PROJECT, REPORTER, ASSIGNEE, CREATOR, issuetype, SUMMARY, DESCRIPTION, ENVIRONMENT, PRIORITY, RESOLUTION, issuestatus, CREATED, UPDATED, DUEDATE, RESOLUTIONDATE, VOTES, WATCHES, TIMEORIGINALESTIMATE, TIMEESTIMATE, TIMESPENT, WORKFLOW_ID, SECURITY, FIXFOR, COMPONENT) VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?) (Incorrect string value: '\xF0\x9F\x98\xA3' for column 'DESCRIPTION' at row 1))

The impact here is that if someone who doesn't know where to look to identify the error copy pastes email contents containing an emoji with whatever encoding Outlook / the Windows clipboard / Google Chrome are using into a JIRA field, they will be frustrated and confused as to why they cannot save their issue.

Arabic characters are fine, so I'm assuming this isn't just a high codepoint issue.