Hey there,

Apparently this was a feature in older ReplayMod versions (that's what I understood from reading some forum threads at least), but it would be a very good (and in my opinion important) feature to be able to hide invisible armorstands in replays. I'm currently working on a project and the armorstands used for holograms and other things being visible is kind of ruining the cinematic.

This never used to be a feature afaik (Edit: You're right, there used to be an option for this before I started working on the mod. But with below commit, it should now be the default behavior and no longer be configurable.)
The camera during a replay is technically in spectator mode, hence why you can by default see invisible entities. I think there was some code added at some point to change that such that you can no longer see them (which is probably what you read about on the forum).

Maybe that code isn't working as intended in your case. Which specific version are you using? Are you using any other mods? If so, does it behave properly without them?

Edit: For reference, this is the commit adding said changes: d8e9f62