
Hi @MichelGerday,
I am afraid that it is a default behavior of Yammer. Without posting messages via flow, on Yammer portal, I just post message under my name, there would be not counter beside the Yammer group. While the counter will appear when my co-workers post message in the group.
Just as you mentioned, it is supposed that I posted the message.
Hope it could be your reference.
Best regards,
Mabel