D.Mon has a "free look" shield feature like Rein's, buried in her advanced hero settings
I haven't seen anyone talking about D.Mon being able to free-look while shielding (like Reinhardt), so I suspect not many players have found it yet. It seems potentially pretty strong with her omni-directional booster movement, to navigate more precisely while continuing to block.
She can't do it with the default settings, but if you go into D.Mon's hero settings and turn on Advanced > Use Surging Strike with Quick Melee and keep Use Over-the-Shoulder Third Person Camera to the default value of "off", then holding primary fire while shielding allows you to freely turn the camera without turning the hero. She has tank controls in free-look by default, but you can turn on Movement Relative to Camera During Power Barrier Free Look (which Rein has on by default).
In case you don't know what I'm talking about, or just want to see a demonstration, I slapped together a quick video. It covers the free-look mechanics for Rein and D.Mon, and how they interact with settings (and perk choice, for Rein).
Edit: I was focused on the existence of the free-look feature, because it's extremely non-obvious that the buried Use Surging Strike with Quick Melee unlocks it. I only figured it out because I noticed Movement Relative to Power Barrier During Free Look.
But, as others have pointed out, another major benefit to Use Surging Strike with Quick Melee is preventing accidentally using Surging Strike when trying to swing after shielding. In the video, I demonstrate the analogous setting for Reinhardt's Shield Slam major perk, which has the same benefits. I think both of those settings were inspired by Brig's Quick Melee, which swings her mace just like primary fire, but without the possibility of triggering Shield Bash.
Here's hoping that Vendetta may receive a Quick Melee option for Projected Edge too.
More edits to fix typos