well, what is your opinion based on? don't get me wrong, this really is a question!
As I wrote before, I'm a novice, but I've been reading a lot about SEO. And it seems that more is not better. A few strong (i.e. of good quality and length) pages seem to work better than more not so good quality pages. For example, take a look at this
study by Ahrefs. So I figure, if I keep the rest of my website to be of good quality and updated, it may be better to noindex my board and just use the discussions held there as a valuable input to the rest of my website. But I haven't decided yet on what to do...
And there is also the more technical side. I feel that phpBB could do better when it comes to telling bots which links to follow. For example, why are login/register/new topic/reply etc. links dofollow links? (see the last paragraph
here).
And, since we're discussing SEO, what do you think about
robots.txt of arstechnica.com? They've blocked lots of paths of phpBB. Maybe this is a good idea for blocking bots from visiting links unimportant for SEO.
Marek