Not sure what is happening here; earlier today, i was creating and deleting keyframes totally fine. Now, when i highlight keyframes and press delete, i am instead prompted to delete my figures. Reloading the scene does no justice, either. Is there a keybind to do this instead kf having to highly each individual frame and clearing keybinds? This is not ideal as itll delete all my frame for every figure in a scene.

Two points: Sometimes the object which has the focus is not very obvious in Poser, whether it be an actor in the scene Preview, or the library palette, or the animation palette. They all respond differently to a delete keypress and being sure exactly what has the focus is important. The other caveat/question is that the first keyframe at frame 1 can never be deleted. Poser just won't do it. But I'm confident that's not what you were referring to.

I've also noticed that the animation palette will not always retain the previous selection rectangle for keyframes after an action. Apart from prompting you to delete an actor or figure, it can occasionally be mysterious why the keyframes previously selected weren't deleted, until you notice that they got deselected somehow.

The Delete key does not delete Key Frames never has. You have to use the + and - buttons in on the animation toolbar. If you use the one on the Pose window then it adds and deletes all key frames on all items. Using it on the animation palette you can choose to have it effect everything or just the currently selected body part. If you have it set to selected then you can collapse a body part down and delete Key Frames for everything on the part (which could the body which removes all Key frames for a single figure but leaves the other figure along).