Also, I was never a fan of the whole "subforum" thing that so many modern boards have. Like, not all fora are listed on the index anymore, you have to click on some fora to reveal other fora. Isn't that what the categories are for, to group fora? With sub-fora, I often forget that a forum even exists, much less remember to check it regularly.
And boards that default to E-mail notification. Ugh. I don't want you to spam up my E-mail account with "Someone replied to your thread!" "You have a new private message!" "Someone else posted in a thread that you posted in back in October!" "Someone looked at your thread!". If I want to know those things, I will check the actual board.
I prefer AcmlmBoard's single "Edit profile" page over the complex multi-page user control panels at most boards. I don't want to have to figure out which of 15 pages has the option to change the time zone or which one lets me turn off the damn default E-mail notification. To change your sig on a phpBB, you have to go to User Control Panel, then Profile, then Edit Signature, waiting for each page to load. Here, it's just Edit profile and scroll to the signature field
Plus, what other board has post layouts, posting syndromes, post numbers being given as xxxx/yyyy, HTML support, and all kinds of other things I'm accustomed to AcmlmBoards having?

I love the coloured usernames, but most boards that have them only use them for the online users list. At non-AcmlmBoards, I'm constantly going "wait, that user is a moderator? That one is banned? I didn't know, their colour is not different!".
And, possibly above all, I grew up at Acmlm's and have so many good memories of it and of many other AcmlmBoards
Edit: Oh, and the sidebar goes on the
left, please and thank you. Not the top or the right. Sheesh. I guess it's like the switch from menu bars to ribbons. Why mess with something that isn't broken?
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TKB Super Mario Bros. •
TKB Super Mario Bros., Volume II