However, /* . . . */ is definitly supported in SQL. Especially in hql-editor, multline comments are more sensefull than one-line-comments.
http://publib.boulder.ibm.com/infocenter/idshelp/v10/index.jsp?topic=/com.ibm.sqls.doc/sqls36.htm
Will the issue reopened? The hql-editor does not provide to have multiline-comments.