Thought of oneself will destroy all other thoughts

In a comment on my previous article, Is there more than one way in which we can investigate and know ourself?, a friend called Venkat wrote:

Given that the ego/mind is non-existent, and just a thought that pass across the screen of consciousness, what is it that choose to be attentively self-aware? Pure consciousness just is, and the body/mind/world are just thoughts/perceptions that flow across that screen. So the thought to be attentively self-aware is just another thought on that screen. I am struggling what is it that then directs attention. Apologies if I’m not being very clear.

When I read this comment, I noted it as one that I should reply to, but it soon led to a thread of more than thirty comments in which other friends responded to and discussed what he had written, so in this article (which has eventually grown into an extremely long one) I will reply both to this comment and to a few of the ideas expressed in other comments in that thread, and also to many later comments on that article that were not directly connected to what Venkat had written but that are nevertheless relevant to this crucial subject of self-investigation (ātma-vicāra).