What is the green/red drag line in Altium?
I asked the Altium support if there is either a way do disable this feature or to get a detailed description to understand what it does.

This is loosely translated from the German response:


  If you are seeing green/red lines when placing components in the PCB document, this can be interpreted as follows: It is a kind of feedback from Altium Designer regarding the length and position of the connecting lines. Red lines indicate, that there is still a better position available with respect to intersections and connection length. Should the line show green, then this is an indication that the length of the connecting lines is well matched.


I am not really satisfied with that response but I could just disable .... oh wait.


  However, there currently is no way to turn off this mode during placement.


Well, at least its a great example of implementing a feature that no-one needs because its not even documented how it works :)