Custom? But why? Don't get me wrong, it's cool to do your custom stuff. I often do that myself, but sometimes it seems to be a case of "reinventing the wheel". Often you will have to solve problems that are already solved in established products.
New website is hosted scalably on Azure, it's hard finding a forum that:
- Runs on asp.net
- Scalable in our infrastructure (we utilise Redis heavily)
- Can seamlessly integrate with our membership system without having to glue them together which was a huge pain point of the old site
- Ties in with our email and alerts system
I get the pro's of not re-inventing the wheel definitely, but a lot of the components of the forum were already written in other parts of the website so was a case of just utilising them in different ways.
Using prebuilt has the downsides of having to hack and glue a lot of stuff together, which also makes installing updates difficult when you've made big changes to it (pain point of old forum as well).
Edit: And yes, mobile rendering is on the list.