The title says it all ! PLEASE add automatically a line to separate a reply from an email body. If one have a signature, like I do, then the line should go directly under the signature. If you argue that the line feature that exist is at the user discretion to add or not, it is a poor excuse. If I want it then... it is needed. If you insist then... I ask that you then make it a customisable feature in the reply properties of Thunderbird to be check or not by user discretion.