I believe that there is a desire that individuals and groups of individuals have to not have to interact with or even view comments of another community. Currently, only communities are able to actually make that desire a reality. If it was good enough to simply ignore all of the comments and pretend like they aren't there and block every community that I see pop up then why even allow instances to block other instances? They could do the same thing. But of course it makes sense to be able to block other instances because from a UX point of view the user has some desire for a functionality and so the functionality is added. And just like groups of individuals can have a desire to not interact with another community, a single individual can also not want to interact with that other community. Why should I have to deal with constantly blocking new communities and trying to just ignore comments in order to use the site? I would rather just not use the site at all.
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.