When placing ground vias to connect to my components Altium sometimes removes the via after connecting it with a trace to the pad.
In the following image, if I was to complete this trace. Altium removes my via and leaves the trace there...
(This is a fairly simple design with only two layers. The bottom layer functions as a GND polygon.)
I do not know if this is a known function of Altium, or if I am missing something.
edit: Altium does not always delete my vias. (I cannot find a pattern in the times that it does happens though.)