I am in awe that this feature DOESN'T yet exist. It's been making me crazy and I have to do two times the work on my To Do lists in Evernote than I would if I could quickly highlight and strikethrough completed items. I'm having to cut and paste them into a "completed" column for workflow tracking/archival. SO ANNOYING. Evernote, can you make this happen ASAP? Pretty please? Thanks.