The instructions are quite clear, as soon as you score 90% or better you should add another character.
The programs could (and probably should, if it's that important) do that automatically.
I don't know about that - the scoring is open to interpretation at more than one level. When I said that the instructions are clear, I was referring to the percentage at which you should add a letter.
It is possible to get a total score of more than 90% and at the same time get less than 90% on one or more characters. Some reasoning may be required. For instance, if you scored close to 100% but missed the only M that was sent - you should move on even though the individual score for M would be 0%
Some programs don't offer grading at all, others have it as an option. JLMC grades in real time, I don't think any of the other programs do that. Even when grading happens in real time, you may disagree with the score.
There is also something to be said for not forcing your own ideas on people. While I believe that Koch's method is the best option for learning Morse code, I created JLMC in such a way that you can use many other methods for learning if you want to. I don't believe in using visual aids for learning Morse code, but some people want it so I included it (as an option).
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K4NL Sid
justlearnmorsecode.com