Sepplord wrote: They don't add other GvG-groups, because they don't want to get added....not because they in general don't add
That was true for a lot of groups, even well established high rr ones, sadly. But there is another motive to consider for some kind of marker. With the latest changes in /gvg rules, a visible marker wouldn't be too bad for ensuring you don't add on a /gvg fight as a listed group by accident and violate the rules doing so, but tbh, if it's an ongoing fight I'm usually driving my group away, regardless of clear /gvg fight or not.
Apart from that, by ensuring the visibility you might promote more groups to use /gvg toggle because you minimise the risk of punsihment for an "accidential add" on another listed group. Recognising established groups is easy, but new groups/pugs sometimes get overlooked.
Regarding rolling solos etc., being visibly marked by something as a /gvg group might promote more respectful behaviour, but I'm not really sure of that. I fear that the server has been a red-is-dead feast for too long to have a real chance of establishing that kind of respect towards different playstyles.