The Blackwing is a remake of the Eberhard Faber Blackwing but it's still a pencil. Pencils have a few assets, though: 1) Shading. Shading with a pen is a bitch. 2) The act of sharpening is a nice ritual. 3) Erasers are way handier than strikethrough. More aesthetically sanitary. And I say that as also a lefty. I think anyone who has any tradition of mechanical drafting appreciates the pencil. Bitchin' lead holders, super-good compasses, powdered eraser, drafting dots, french curves... Pens? Pens are what your assistant uses once you've actually designed the thing. Pens are for acolytes and calligraphers.
I kind of figured that if you were recommending it it had to be The Best Pencil Known To Man that experienced none of the typical Pencil Problems. ;) I actually favor a (preferably one)-line strikethrough when I edit/markup because then I can still see what I've changed, both to and from. I think some teacher made me start doing it that way a long time ago. Erasing is like deleting w/a keyboard, except I can't Ctrl-Z my way out of it. The strikethrough doesn't demonstrate so well in the picture I put up above because that's literally my brain-tires squealing - I should've just walked away from the page - but you know. Sometimes you wanna see how you said it before for a while after you change it. Occasionally I revise a line, go to re-type the poem, and decide I like the original version better. It happens, though I wouldn't necessarily say often. Aesthetically, yes, you should erase over strikethrough. But why not just copy over to a clean sheet at the end if you're worried about how it looks? (Waste of time, I hear ya.) Shading's a very good point. Cross-hatching with a pen doesn't even begin to cut it.