Hi Jhana acarya
Mindfulness and clear comprehension is clearly defined by the Buddha in the quote I posted, and in the first paragraph of the samadhi sutta quote you posted. However the second paragraph refers to the ending of effluents (aasava)- ie full enlightenment. The practice mentioned in that leads to (mostly) insight by focusing on the five aggregates, in a framework approaching that of the four noble truths (object, origin, passing away--complete release from object). This is appropriate as ignorance is the last fetter to be lost.
I agree that clear comphrehension (mindfulness of arising, persisting and subsiding of the four foundations) will eventually lead to non-grasping and the other qualities you mentioned.
I am not trying to be pedantic here! I think we need to have consensus when we use a technical term from the suttas otherwise communication can flounder.
In my opinion vipassana begins when we are knowing and seeing the one of the three characteristics and it is leading to even minor degrees of detachment through insight. Anything other than this can be just a samatha/tranquility process. It helps to be clear about what it is not:
Vipassana is not mindfulness (mindfulness alone can lead to samatha)
Vipassana is not watching an impermanent object (doesnt necessarily mean that the observer is grasping that insight)
Vipassana is not watching multiple objects (that also can lead to just samatha)
Vipassana is not synonymous with satipatthana (it contains the seeds of developing both samatha and vipassana)
I think it is important to be clear about what vipassana is otherwise we may do one thing thinking it is something else.
Vipassana can be reached rather quickly and reliably by using a contemplation/yonisomanasikara.
Discursive thoughts in vipassana are best dealt by developing samatha samadhi to a deep degree (ideally jhanic). This will make the process a lot smoother- any insights will sink in deeper-the process will be faster. Also if using a yonisomanasikara method it will stop the contemplation from becoming merely discursive thinking.