Ok, that's an initial version complete. http://mybrillgamesite.com/files/RHDNAddIn.crx
It's minimal, so minimal but it has the ability to hide threads based on title and now that I've got that in I'll look to add more functionality sooner and faster.
For now it is Chrome only, multi-browser support is high on the priority list but I was using Chrome at the time so it got priority. Next is Firefox then IE. If others are needed please ask.
It is hosted directly on my site, here is a direct link: http://mybrillgamesite.com/files/RHDNAddIn.crx
you'll be given a warning about crx files harming your computer and this is because really it should be released via the Chrome Web store and that is also on the todo list after getting some more features in. (Not cause I'm selling it, just cause it is the 'proper' way to release on Chrome.)
To use it in the current form all you need to do is drag and drop the RHDNAddIn.crx file anywhere inside Chrome. It'll ask if you are sure and warn you it can edit data on romhacking.net, say yes and it'll install.
To uninstall go into Chrome's settings -> extensions and click the bin icon next to it.
Like I say it is pretty minimal, I won't explain how to use it cause there is only 1 dialog box and the instructions are in it but it allows the hiding of an unlimited amount of threads by copy and pasting their title in full onto new lines for each one. Simple.
Something that is pretty cool, but may be removed in future versions depending on cross compatibility issues, is that your settings will persist across Chome browsers. So if you install it on 2 computers you should only have to enter your settings once and they'll be saved to both. Nifty.
I'll add user hiding, emphasizing, puppies and other cool stuff soon.