My .02 worth...
I must say I've never really considered these comments strips as a "forum". To me a "forum" is a site usually powered by something like SMF or phpBB where posts appear immediately and, if unsuitable for the forum, end up getting deleted by a moderator (and possibly getting you warned / banned into the bargain).
This to me is more of a letters-to-the-editor system, such as you might find on any newspaper. In a forum, I might post 20 or more times in a thread while back-and-forth-ing in a debate with someone. Here, I rarely post more than one comment in any thread, the same as any other newspaper site. Only if some twat replies to me with a comment that really deserves a poke in the snoot will I post a second or third time in a comment thread.
It's also why I use my real name here, the same as any letters-to-the-editor column, for legal reasons, rather than using the net handle I use everywhere else.
That said, El Reg is a lot more liberal with its comments than any other newspaper I've commented on, and it's more liberal than many of the forums I post in. Some of the comments I've posted (and that the mods have published) here would have gotten me banned on most of my forums. In fact the only place I've found where I can be even more offensive or abusive than on El Reg is 4chan!