Flagging important chat messages

This is a bit of a crazy request for something I've never seen on any other platform, but it would be incredibly useful for us, and I suspect others too.

Quite often, we will have long discussions in chat about an issue (or in a thread). Having all the chat messages attached to the issue is very helpful, but sometimes important decisions or posts get lost among more casual messages in a long discussion (some of us are very verbose!)

We've informally taken to solving that by writing things like: "[DECISION] as discussed, the button color will be red." or "[UPDATE] first draft is done an on the staging server" and then reacting with an emoji to the relevant message, so that these messages stand out in the conversation and we can find them more easily later.

What would be very nice would be some way to actually filter to just show such messages. Something like the "pin" feature but instead of pinning the message it just marks it as important.

What would be even better is if all of the messages in-between the ones marked as important were automatically collapsed. That way you could see a quick overview of the conversation and key decisions, but expand one of the collapsed regions to dive into more detail and understand the background of the decision (messages after the last "important" message would not be collapsed, as they would be part of current active discussion).

It seems it would make sense for this to apply to threads, issues, and code comments, but not to DMs or messages posted directly in a channel. 

I realize this is a radically different feature suggestion, but I hope you'll give it some consideration anyway. It would dramatically improve the usability of the platform for us (and I suspect many others). The main issue we have is that we are an international team and aren't all native speakers of the same language, so quite often "skimming" through a long chat thread can be even less efficient. Having a way to call out these important updates and decisions in the chat on an issue or thread would be incredibly useful.