#FediTips (or perhaps #FediWarnings?):

Something I discovered the other day on accident is in Mastodon and derivative software, if you are sending someone a DM, and you spontaneously tag someone in the middle of the message, *that person now has read access to the DM in which they're mentioned*. This is a neat feature if you're using it on purpose but could be awkward if you're just trying to link an account and suddenly that account can see you talking about them…!