Bug 23968 Abusive check on task tags
2.1M1 Java UI ensures that task tags are valid Java identifiers. Why is it so ? JDT/Core supports any type of tags. In particular, "TODO:" should work fine, and was one of the mentionned tags on the original feature request.
org.eclipse.jdt.ui/ui/org/eclipse/jdt/internal/ui/preferences/CompilerPreferencePage.java
try {
			dialog.run(true, true, new IRunnableWithProgress() {
				public void run(IProgressMonitor monitor) throws InvocationTargetException {
					try {
						JavaPlugin.getWorkspace().build(IncrementalProjectBuilder.FULL_BUILD, monitor);
					} catch (CoreException e) {
						throw new InvocationTargetException(e);
					}
				}
			});
		} catch (InterruptedException e) {
			
		} catch (InvocationTargetException e) {
			String title= JavaUIMessages.getString("CompilerPreferencePage.builderror.title"); 
			String message= JavaUIMessages.getString("CompilerPreferencePage.builderror.message"); 
			ExceptionHandler.handle(e, getShell(), title, message);
		}
	}		
	
	/*
	 * @see PreferencePage#performDefaults()
	 */
	protected void performDefaults() {
		fWorkingValues= JavaCore.getDefaultOptions();
		fWorkingValues.put(INTR_DEFAULT_COMPLIANCE, getCurrentCompliance());
		updateControls();
		validateSettings(null, null);
		super.performDefaults();
	}