It is very common to allow the same action with double click and drag as works with click and drag, but it selects whole words. I continually find myself trying to do this with PDF documents only to find I’ve only selected a single word and the drag does nothing.
Why not work like the majority of programs and support double click and drag? It would make using Sumatra much more like the rest of the world and not make the user think about Sumatra differently.
I will say I am very happy with Sumatra. It’s a great program and I’m glad it was developed. It just has a very few nits that I don’t care for.