When you select a particular customer, you don't know beforehand if there is going to be a popup or not. People might continue typing or simply press 'Enter' intending to dismiss the history screen, but instead dismiss the 'important' patient note. I suggest keep the 'c', to make sure it is not inadvertently dismissed, and only dismissed on purpose.
If others think the note should be dismissed using any key or the 'Enter' key, then perhaps it is not an 'important' note, and should be put as a regular note without the popup?
Someone may be able to provide an example where the note is 'important' but still needs to be dismissed accidentally.

I would like to see any key be able to dismiss the important patient note popup - the popup is "in your face" enough and it slows workflow to have to press a specific key to dismiss it.