When an issue is created with a '<' [smaller than] sign in the summary, no problems arise. If though the issue is edited, an update results in the following error:

Form Errors:
Exception occurred: com.atlassian.core.AtlassianCoreException: Error in action: com.atlassian.jira.action.issue.IssueUpdate@2119432, result: null: SQL Exception occurred on commit (I/O-uitzondering: End of TNS data channel)

If the sign is replaced by a textual representation, the first word of the summary is always scrambled like:

që@it possible to use smaller than signs

For:

Is it possible ...