I think their javascript is interfering with hash links. This is one of the many issues that will be resolved once I have the time to write a PROPER skin for these forums, instead of this current sloppy paintover.
I've actually started writing said new skin for SMF 2.1 under the release candidate. I am NOT planning to deploy the RC here as such things are generally not for production, but if the issues with the badly outdated 2.0.x continue to be an issue, I might risk it.
In any case, by the time SMF 2.1 hits "final" I should have a custom skin lacking these problems, particularly since half the stuff they're using JavaScript for is going in the trash.
Pretty much growing pains, it's been 8 years since I last ran a forums. I went with SMF just because I knew it better than others, letting me get this up, running, and usable in mere minutes the moment I read about codingForums being shut down, which was really the last straw when it comes to web dev forums... What with DigitalPoint being so painfully mercenary, and Sitepoint not only having the ugliest most useless forum interface I've ever seen, but also being a den of suck-ups and sycophants where any dissension is stamped out like a petty dictatorship. ANYTHING to keep selling their shoddy books promoting things -- like JQuery and bootcrap -- that have zero business even being used in professional development.