I'm still not sure about where the boat story came from, but even 5 years ago in this thread people were speculating whether or not they liked each other. There was also this interaction that someone posted in the same thread where Anisa was defending the word "coon" and Katt, Max's now wife, disliked that and said something to her on twitter about it.
It's hard to pin down the boat trip stuff - I remember reading about it as clear as day but can't find the exact passage (nothing but love to the lolcow.farm people but imageboards are shit), but it's not the only point they bring up. For example there's also this tidbit about a Hawaii trip which I don't even remember. It might even be the same trip.

Unfortunately, even from anisajohmareciepts' old accounts there are precious few screenshots of this early period where everyone characterizes Anisa's relationship with Max and Kat as bordering on openly hostile, though I can believe it, because Max used to be a bit of a moralfag on Twitter and would not have taken well to Anisa's clownish attempts to ape her then-boyfriends sense of humor.
It looks like a small ceremony, but how close is Dolan Dark to these guys? Even if it was a private ceremony, I think if Ian was in good standing (or wasn't dating Anisa), he would've been invited. Just making an exception for Franku kind of comes off like they're clout chasers, which is definitely not the case.
Thing is, operating off the belief that iDubbbz wasn't invited because he's a lolcow or because of Anisa (as opposed to the fact it was just a more private affair and Joji just took the opportunity to drop in) says more about Max and/or Kat than it does about him. Otherwise, if what everyone is assuming is true, then Max and Kat, both comparatively sensible adults, 6 years on, had to have found Anisa to be
so intolerable that keeping her away was worth saying no to an old friend and the inevitable awkward questions it would raise. Of course that's not impossible, but personally, I think it's more consistent with what we know about Anisa that, if iDubbbz
was invited,
she would have been the one who would have begged/convinced/coerced iDubbbz into not going, because what would her ego have to gain from being seen surrounded by people at the much happier, much classier, much better attended not-in-Vegas not-presided-by-Elvis not-whored-out-on-social-media wedding of two not-trashily-tattooed people she's jealously tried to skinwalk as? We know she's prone to bouts of crippling mental health issues when confronted with events not about her.
As for Dolan Dark, he's been there since the old days, but like HowToBasic, how close he was with everyone is hard to work out since he's so private. But were it meant as a partial YouTuber reunion, I'd think he'd be part of it.