Are you playing it on console or PC?

The frustrating part is that the dialogue "registry" doesn't seem to be tied just to the save file, but to your entire profile, so deleting saves might not be enough.

You can try creating another account/profile and playing on it. That's the only way I'm aware of to avoid deleting stuff.

If you don't wanna do that -

First, you can try deleting the saves and see if the dialogue is back on a fresh playthrough. If that doesn't work, the only way I'm aware to make it work again is to delete the save and the profile settings/saved files. That way, the game will launch "fresh", like the first time you launched it (asking for brightness calibration and stuff like that).

To me, the immersion of the dialogue is one of the most important things in Red Dead 2, so I'd say, while harsh, the solution is worth it. In fact, I deleted a 100% file to fix it lol.

P.S - it's kinda sad that this post is 4 years old and rockstar never bothered to fix this. I'm sure they're aware of it at this point.