When Apple released OS X Yosemite and iOS 8, they added a bunch of new features to Messages on both platforms. One of those new features was the Details panel, which gives users a ton of functionality; the ability to change the name of a group message, add and remove contacts, turn on Do Not Disturb on a message-by-message basis, leave a conversation, see the location of anyone who has shared it with you, and view a list of attachments (mostly images) shared within the message. All of these features are awesome and make using Messages a ton better than it was previously.
One thing I find myself doing all the time, however, is thinking, “So-and-so sent me a link a few days ago, and I’d like to pass that along to someone else.” Have you ever tried searching for a URL in Messages? It’s never a very productive process for me. It seems like that Attachments section of the Details view could offer a list of links from the conversation. It could also include phone numbers, addresses, and locations; basically anything that the OS turns into a link/button.
Secondly, I find it strange that Apple built that—awkwardly-placed—Safari Shared Links panel, which aggregates links from your social feeds, but they don’t include their own Messages app as one of the options for it to cull content from. I could see that being a huge benefit if you couldn’t remember who sent the link to you, because that would have everything in one place and searchable. I really can’t think of a good reason not to give users both options.