Who positions their speakers straight ahead (zero tow in) and why.

Reference 3a de Capos have no toe in. Tash recommended that and I've found out it's true. When I toe them in they lose definition. 

It is very important to point your speakers directly forward........This only applies to married audiophiles..everyone else can ignore this advice

This question has to do with your room size and your speaker design. In my very small room, I have experimented both ways, toed in and straight ahead. The toed in position works fine, but I notice that I do lose some imaging specificity. I also find that on some recordings, the brass instruments can be a little too much in your face, so for me, straight ahead is the answer.

What's a "hot tweeter"?  

If you have the time & never done it before.. position your bookshelves so they criss cross past your outside shoulders. L speaker across rt outside shoulder, etc.