I do like txt format, often called "plain text". I agree with Joel Spolsky that, strictly speaking, There Ain't No Such Thing As Plain Text. "If you completely forget everything I just explained, please remember one extremely important fact. It does not make sense to have a string without knowing what encoding it uses. You can no longer stick your head in the sand and pretend that "plain" text is ASCII. ... If you have a string, in memory, in a file, or in an email message, you have to know what encoding it is in or you cannot interpret it or display it to users correctly." (See Joel on software.) You don't even need to be a programmer to know this. You'll find out the truth of this statement, if you use a software program that expects UTF-8 and try to open a text file that is encoded in ANSI. I know that there are some text editors that have under "save as" the entry "normal text file," but Notetab which I use for most of my text needs has four different entries under encoding. But all that being said, "plain text," as compared to "rtf" or proprietary encodings, still makes sense. As long as you remember that it really means only "minimal encoding," it is no more harmful to speak of "plain text" than it is to speak of "the rising sun."
One of the reasons I like the "Todotxt" format is that it is plain text. It took a long time for me to warm to it. The reason for this was that originally it consisted of scripts meant for the command line. And I do not like the command line. It isn't so much that I am scared of it, but rather that it does not appeal to me. It reminds me of the days in which you had to type DOS commands for any program to do anything. I am glad these days are over (even though I amaze even myself that I still remember the commands when there is a need).
jrnl is a program that promises you to be able "Collect your thoughts and notes without leaving the command line." In other words, it is a journal application. My problem is, of course, that I would first have to open a command line and then leave it as soon as I am done with jrnl.
That is why the other advertisements leave me cold: It is "human friendly" because "jrnl has a natural-language interface so you don't have to remember cryptic shortcuts when you're writing down your thoughts." It "Future-proof" because Your journals are stored in plain-text files that will still be readable in 50 years when all your fancy iPad apps will have gone the way of the Dodo." It is "Secure" because you can "encrypt your journals with the military-grade AES encryption. Even the NSA won't be able to read your dirty secrets." It is "Accessible anywhere" because you can "sync your journals with Dropbox and capture your thoughts where ever you are." It is "DayOne compatible" and allows you to "read, write and search your DayOne journal from the command line" etc. Well, I like to use DayOne the way it is intended to be used.
Still, others who are more inclined to be luddites (no disparagement intended) might like it.