Is it possible not plotting a Tag value when its quality is bad, in a historical E3Chart?

Yes. By using scripts, it is possible to configure an E3Chart to perform this.

Set Pen = Screen.Item("E3Chart1").Pens
Pen.Item("Pen Name").ShowBadPoints = False

Notice, however, that this solution is only valid for historical values. At run time, this value is always plotted, regardless of Tag quality.