I think Ghosting I'm a group setting is something the GM has to handle, since there is so many reasons their player might not be posting. Now handling it aggressively like someone has done to me before is by far unacceptable, now it should just be courtesy to say "yeah nah I'm just not feeling it so I gotta drop out" like I or anyone else should say if they just don't have the time of day or motivation to be in an rp. It just makes sense to say something rather than nothing but it isn't always as simple as that.