Thank you for a detailed and specific review of MJ. This is very useful.
The issues you raise are well known. I suspect that a lot of people give MJ a break because of the low cost....
There [are] better VoIP providers available, for not that much more money.
That issue is called talk-off and can happen with other providers too. It is more common with female voices.
The other party often hears tones that they say sounds like I am hitting my phone keypad, which I am not.