When you don't have a secure E2EE coms channel with someone, these services enable creation of a one time link that you can send over SMS/email. If the intended recipient is unable to open the link, you know your coms have been intercepted.
But who said they don't backtrack every note with sender IP index? I would do that, imagine the temptation to store all the secrets making a centralised secret notes service
Burnernote code is FOSS if you want to investigate how it works. As for IP addresses, you are probably aware of TOR and VPN's if you want that additional layer of obscurity.
There are numerous problems with that. First – why on earth i need to believe that the source hosted on Github is actually used to build burnernote.com bundle? The bundle is highly minified and obfuscated and the only way to check that is to build the same bundle on your machine and checksum. Did anyone ever did that? Another big issue is since it open-source – it relies on 1000 open-source dependencies, any one of them can be compromised, and the changes to them happening quicker than you can audit them all
