A new ouroboros in the tech world has emerged: There's now an AI tool to "undo" AI writing. Sinceerly is a Google Chrome extension to edit AI-generated (or human-written) emails. The aim is to add in errors that are typically scrubbed away with AI tools and change some of the obvious AI text "tells," like the phrase "not just X, but Y." Em dashes fall into the latter category, too — but as a longtime writer, I'm fond of them and abhor how it's apparently become a signal of AI. Regardless, Sinceerly will kill the em dash, as it states on its website. The tool has three modes: subtle, human, and CEO. Each render text more and more casual, where "CEO" mode doesn't even have correct punctuation but does tack on "Sent from my iPhone," of course. Mashable Light Speed Sinceerly is free for three email rewrites and works within Gmail. But if you want to pay $4.99 per month, you get unlimited rewrites, can switch instantly between modes, and can cache results so you can reopen them instantly.…