OK, here's my list:

First and foremost, restore/recover the years of work by Bagginsbill and Snarlygribbly in those forum posts which had attachments converted to garbage.  Make some effort to show them their work/help/support of YOUR customers and users is appreciated.  This is a moment to go above and beyond.

Give us back the ability to post an example python script or material file as a text file attachment.

Get rid of all the posting icons/nonsense and give me the OPTION to go to an advanced mode with limited HTML markup if I want to.  A simple post with a link or an image shouldn't be as hard as this software makes it.

Allowing simple pasting of a link that STAYS a link.  It should not take a degree in computer science to put a link in a forum post.

Realize your audience is text based, folks simply looking for an answer to a question, usually in a hurry, on a deadline, stuck trying to do something in Poser they can't understand how to do.  Make getting those answers simple and painless and giving the answers less difficult.

TEST the site in multiple browsers and resolve the browser compatibility issues.

Compact the forum post display....the scrolling and scrolling and scrolling is unnecessary.

Remember that different users have different browser setups and window sizes.  The site should recognize the monitor size and make an attempt to present the best display capable - and that includes spacing.