vb.org doesn't use this mod... that is a different method of achieving similar results. The concensus seems to be that SEO would not be hurt with the mod, however the version you used as an example is unfunctional without javascript (which tmk spiders do not parse). Im really no expert by any means on SEO and spiders so I defer to these guys on that. However I know that I would need a solution that didnt break without javascript
Also, relevant or not to the mod in question... the bottom of the forumhome in the example you linked to has w3c compliant images, but when you click on it, there are 388 validation errors! Now the site you linked to has A LOT of modifications on that page, so any combination of those modifications could contribute to the validation errors, but still... something I would also check out