use of the imperative

Darren, if I remember my Greek, one way to tell the difference between the imp. and 
the Ind. esp. in the 2nd per.pl, is if there is a "me" it is an Imp. if there
is a "ou" in front then it is an Ind.  As for the second part of your question-
it is very valid, the "me" is telling you that what is coming is an imperative
and that the <person/object> must stop imediatly, the action that they are doing.  If however the imperative is in the Aorist  then the "me" with the imperative
is saying "don't even think about doing it!"
Hope this helps, holler if you need more help.
Dan Gilbert
Keene, TX.
May God bless your study.