For my custom model I've introduced multiple message subtypes, each modelling a special points in the business workflow. The subtypes are assigned by overloading "_track_subtype" (inherited from "mail.thread"). This works like a charm.

But... Since we are quite actively using the chatter feature for internal communication, the messages related to these special points in the business workflow tend to get overseen when scrolling over the chatter.

Hence we want to give these messages some optical emphasis, e.g. a different background color or some icon. How can this be achieved?

Additionally: It would be nice to be able to filter the chatter for specific message subtypes. How can this be achieved?