src/Tools/jEdit/src/modes/isabelle-ml.xml

 <!-- Isabelle/ML mode -->
 <MODE>
   <PROPS>
     <PROPERTY NAME="commentStart" VALUE="(*"/>
     <PROPERTY NAME="commentEnd" VALUE="*)"/>
-    <PROPERTY NAME="noWordSep" VALUE="_'.?"/>
+    <PROPERTY NAME="noWordSep" VALUE="_'.?⇩"/>
     <PROPERTY NAME="unalignedOpenBrackets" VALUE="{[(«‹⟨⌈⌊⦇⟦⦃" />
     <PROPERTY NAME="unalignedCloseBrackets" VALUE="⦄⟧⦈⌋⌉⟩›»)]}" />
     <PROPERTY NAME="tabSize" VALUE="2" />
     <PROPERTY NAME="indentSize" VALUE="2" />
   </PROPS>