I recently found this out the hard way. Instagram’s web app has a super annoying popup. To click the comments button for a post, your cursor has to pass over the username, which just happens to launch a profile preview with the “follow” button exactly where the comments button was, causing you to unintentionally follow the account.

I tried to block this popup with uBlock Origin to no avail. No matter what element I selected, it was still there. Finally fixed the problem by deleting my Instagram account.