First of all I should point out that these forums are not intended as “customer service” and are not manned full-time (particularly during weekends or staff vacations) - they are community discussion forums, and some of us try to dive in and help out when we can. So, apologies that you’ve waited for a few days for a response. Regarding the other post, the forums were transitioned from an older system around a year ago, and some things may have been missed around that time.
We should do a much better job of clarifying how and when Cards are displayed in the timeline as part of the documentation, and we will look into that. We often run experiments with different card types, in terms of formatting and display, so it is actually quite hard to definitively say “card type X will appear like this”, for example.
Saying that - I believe that currently we are surfacing summary cards in the timeline on our own mobile apps, and behind a “view summary” link on desktop web. Player cards may behave differently. Since that post was originally added, we have also added native video upload support. So I think native videos and Vines do play inline at the moment, but player cards on most domains may not.
Sorry not to be able to give you a clear answer on this at the moment, but as we work to improve the overall Cards experience things are in flux.
