Okay, I'll just test this thing here so I can see the network routing. Oxycod-one. Aspirin. Advil. Lemsip.
edit. Lol, not spammy enough? And I think I misspelled Oxy-codone the first time. Okay, let's bring in the big guns. Ephe-drine. Via-gra. Vico-din.
And a 403 Forbidden it was. Looking at the network routing, it indeed blocks any posts with spammy words even before they reach the server, it looks at the content and if it spots forbidden words, it just returns a 403, which your browser then renders as the error message. If the server returns a 200, then you get access to the actual site, but otherwise nope. The 404 not found attached means that the server doesn't provide the default explanation file (its status is 'not found').
Basically there's nothing you can really do about this apart from switching to another forum provider, or advising people that when they get this error message, they should look through their posts for any words that might be considered spam. What a crude way of handling things! But I guess it has to be, since spambots often behave like regular users. :/
(Also the forum is really lazy about updated message database queries! It requires a separate refresh to see the new content, and sometimes previously added content seems to disappear when you reload. Talk about skimping on bandwidth.)
edit. are you duckING kidding me it reverted back to uncorrected spelling XDDD)