With a textarea the likelyhood of the value exceeding the maximum safe length...

With a textarea the likelyhood of the value exceeding the maximum safe length for a GET request (which IE8/9 pegs to somewhere between 2k and 5k depending on the context) is too great as to not provide for the checkMethod to be specified in order to allow for POST requests to be used in place of GET requests for form validation

core/src/main/resources/lib/form/textarea.jelly

@@ -51,6 +51,9 @@ THE SOFTWARE.
       If @field is specified, this will be inferred automatically,
       which is the recommended approach.
     </st:attribute>
+    <st:attribute name="checkMethod">
+      If specified, the HTTP method to use for input field will be checked (via AJAX)
+    </st:attribute>
     <st:attribute name="codemirror-mode">
       Turns this text area into CodeMirror-assisted code editing text area.
       This attribute specifies the mode of CodeMirror, such as "text/x-java".
@@ -76,7 +79,7 @@ THE SOFTWARE.
   <textarea id="${attrs.id}" style="${attrs.style}"
             name ="${attrs.name ?: '_.'+attrs.field}"
             class="setting-input ${attrs.checkUrl!=null?'validated':''} ${attrs['codemirror-mode']!=null?'codemirror':''} ${attrs.class}"
-            checkUrl="${attrs.checkUrl}"
+            checkUrl="${attrs.checkUrl}" checkMethod="${attrs.checkMethod}"
             rows="${h.determineRows(value)}"
             codemirror-mode="${attrs['codemirror-mode']}"
             codemirror-config="${attrs['codemirror-config']}">