$node->revision shouldn't be common for all node types

For now you use:

$node->revision = variable_get('jeditable_create_new_revisions', false);
node_save($node);

This is not so good because D6 have "Create new revision" checkbox in "Workflow settings" fieldset in each content type settings.
There should be correct:

$node_options = variable_get('node_options_'. $node->type, array('status', 'promote'));
if (in_array('revision', $node_options) && !isset($node->revision)) {
 $node->revision = TRUE;
 $node->log = '';
}
node_save($node);