As a general rule of thumb, please don't backseat mod.
It's not against the rules, but it is an etiquette thing.
If you really feel something needs to be moderated, click the report button on the post in question and every mod will get notified about it. Then they'll decide what action to take, if an action needs to be taken at all.
It's a little different if you are the topic creator asking for a mod to close your topic, but it's generally preferable for it to be done through PMing, or more handily, reporting your own post and asking for it to be closed.
