Double tap is all that is required.....

Take this thread for example....
Double tap of a post, and it wil not only zoom in the text, but the text will perfectly fit from the left and right sides of the screen....

Then as another example, zoom out, then double tap on a quote within this thread....it will then zoom in on that quote, and not the original thread like the previous example

So its not just zooming in, but also focusing in on the text you have selected, making the selected text fit perfectly from left to right each time