In the short time that I have been here I have seen multiple arguments in the comment sections that have arisen as a result of (in my opinion) lemmygrad users instigating those arguments. I don’t want to be even tempted to join into these arguments by seeing that they exist. And even if I do ignore them all and don’t get rage baited, knowing that they are there has the potential to negatively affect my mood. I will not do that and it would be silly to think that I am alone in feeling like this. Assuming there are waves of people coming from reddit many others will feel this way also and it absolutely will be one of many obstacles that make large scale adoption a challenge.
To counter that, I've seen plenty of lemmygrad users that were friendly and helpful.
I think the thing you have pointed out about users not having more control over instances has created some tension that probably bleeds over into how users interact with each other. You have users who are trying to avoid lemmygrad in their content feeds, which is fine, but have to be very vocal about it in order to get instances to block or remove federation linking with lemmygrad to better match the content these users want to see, even if lemmygrad users aren't breaking any rules. For lemmygrad users, that seems kinda unfair that they're getting excluded from federation simply because people don't see eye to eye with their world view and don't want to see much of the content they post regarding their worldviews. The lack of control given to users to block an instance quietly causes tension that shouldn't need to be there.
I'm saying this as someone who actually went through the effort of blocking most of the active communities on lemmygrad, so I also don't particularly want to see the content but I so far haven't felt like I had a problem with seeing comments from users on lemmygrad. I would much rather have had the option to just block the instance with a single click than spend more time having to find and block numerous communities.
I really don't even have a problem with seeing that particular ideology or perspective in content feeds, I don't like echo chambers so I'd rather get some exposure to different ideas and content even if I don't particularly agree with it rather than having some algorithm drive me into an echo chamber that causes problems in society and on a personal level mental health problems for people. But at the same time, I think that makes me not very fond of an instance that is centered around that identity, I think it encourages poor thought formation and poor personal growth for people to focus too much on what their identity is rather than just address individual ideas as they come on their own merit.
Edit to add: I'm no coder but I at least looked this up on github and here's the issue. https://github.com/LemmyNet/lemmy/issues/2397 In that particular open issue it didn't show support from nutomic or dessalines, but you can see there was a closed issue mentioned in there where dessalines did voice support for the idea. Only problem is there is 163 open issues with varying degrees of priority, and that one has already been open for a long time so it seems like it is considered lower priority than some other issues. Maybe if more contributors hop in it might get addressed.