I do this, both purposefully (on HN) and, in a manner, inadvertently.
Writing an email and saving it as a draft gives me a memory of having sent the message. Occasionally I get asked about emails I've committed to sending, felt certain I already did, and subsequently found them saved as unsent drafts (inevitably because I got interrupted while I was writing).
I wonder how well it would work to have a placebo button that only shows on your own session