@awcntdb but none of that negates what I said, that a plagiarism-dectector will often not pick up the kinds of “accidental plagiarism” you yourself descibed. So sending it through some online detector will not help the honest student trying to check him/herself who doesn’t know the rules. It will just give a false sense of confidence.
And yes, we spend a lot of time teaching these skills in comp classes. There is no excuse for a student not knowing them.