Ian,
Let me address the 2 issues here.
First:
I'd like Discord to be more open to feedback (in general, not talking about this particular scenario), because currently, she only replies to positive feedback, and tries to defend herself against negative feedback, sometime even by insulting the one that sent that feedback.
I went to look at how the conversation started
[2016-09-06 00:01:22] iancudorinmarian: I'm very disappointed in you, Discord.
[2016-09-06 00:01:39] Discord: ‹@iancudorinmarian› what
[2016-09-06 00:01:41] iancudorinmarian: Your way of choosing which people to interview is really stupid.
You and Discord have a complicated, usually playful, relationship in the game/chat and when you lead off acting informal and a little condescending ("disappointed", "really stupid") you are not clearly trying to start a professional sounding discussion where you are giving constructive feedback and she can respond that she will or won't consider that feedback. You are attacking her value and her competency and did not even directly address the actual issue (that you would like her to follow up on her interview promises in a timely manner) until after she already feels threatened. Obviously she gets defensive, that is a very normal response to being attacked. When you lead off a conversation like this, and then the other person gets defensive, you are unfairly holding them to a higher standard than you are holding yourself. Some people can take this sort of put down and still give you a calm reasoned professional response, but expecting that is unreasonable.
Second:
The NL writing team puts in a significant amount of time and energy and for a long time has been very disorganized, which really increases the time an energy required (or quality of the NL) in adverse ways (which is also compounded by the main NL writer also trying to General a team in War). Per a recent discussion with Discord (prior to this thread) they don't even have a post that lists all previous DIotM and CIotM for them to reference to avoid repeats. I'm guessing that there is also no record of who has been interviewed and when.
The newsletter is a service to the community provided by volunteers, and when volunteers do a bad job at something, it usually means they need help. If you insult or berate people who volunteer (or their work) they quit, which has been a chronic problem here on EtG (and in any other volunteer organization, of which I have worked with many). We want nice things, people volunteer to do them, others in the community harass or insult them and then they leave because why work for free and get angry or hurt over it. If you want people to stay and keep volunteering to do things like be a NL, and you see they are doing a bad job, try asking how you can help.
I'm sure if some people pitched in to help organize a history of important NL columns (CIotM, DIotM, Interviews) it will save the NL writers time and energy they can use to better do other parts of the job. Maybe add another NL staff during wars to help split up the work better since it is a busy time for most of the community.
Ultimately we all want a nice newsletter, we want people to keep their promises, and we don't want people to get burned out and quit. The best way to achieve all those things is to ask them if they need help, have people step in to do little things to make it easier, and to precede any feedback with a thank you.