When using the /label quick action in a reply to a comment, the 'Added ... labels.' message doesn't show up

I'm sometimes using replies to comments instead of just adding a new comment to make sure that the reply ends up in the correct hierarchy of an issue's discussion.

I found that when I add labels to the issue by using the /label quick action there, then this works and the labels are added, but the

Added [...] labels.

message does not appear anywhere (at least I haven't seen it appear anywhere).

This is happening over on https://gitlab.gnome.org - can't try if this happens on gitlab.com as well, as I can't use /label here.