Java "this"-keyword marked as static in eclipse content assist

The code doing this is in org.eclipse.jdt.internal.ui.text.java.ParameterGuesser

// add 'this'
if (currentType != null && !(fEnclosingElement instanceof IMethod && Flags.isStatic(((IMethod) fEnclosingElement).getFlags()))) {
  String fullyQualifiedName= currentType.getFullyQualifiedName('.');
  if (fullyQualifiedName.equals(expectedType)) {
    ImageDescriptor desc= new JavaElementImageDescriptor(JavaPluginImages.DESC_FIELD_PUBLIC, JavaElementImageDescriptor.FINAL | JavaElementImageDescriptor.STATIC, JavaElementImageProvider.SMALL_SIZE);
    res.add(new Variable(fullyQualifiedName, "this", Variable.LITERALS, false, res.size(), new char[] {'.'}, desc));  //$NON-NLS-1$
  }
}

The key thing in that code is

JavaElementImageDescriptor.FINAL | JavaElementImageDescriptor.STATIC

as the flags to JavaElementImageDescriptor which is hard coding the display of the static and final overlay images. So these are always displayed for this.

As to why that was chosen the code doesn't give any reason.