We don't have the button for it here but the option is still available! You just have to type it in manually. The code for strikethrough is [ s ]your struck text here[/ s ]. You just need to remove the spaces to have it show up, like so:
Nova sekritly wants to make out with Laura Roslin.Tada!
You can get additional tips and see all of the available codes by clicking the BB Code Help link right below the Clickable Smilies box when making a post.

As for the View New Posts bug, I'm trying to find some help but it's slow going. IF had a datacenter outage last weekend and the search feature on their support forum is turned off while they make sure everything is totally back up and running. It's taking me a while to slog through all of the threadsthe trying to find what I need.
However, IF recently bought out ZetaBoards and IF users have the option of converting. ZB has better security, more features and fewer bugs so I think I may put our board into the queue to be converted. Better now while we don't have that many posts, just in case some data is lost. But all of the other conversions seem to be going well so I think it'll be okay, although I'll probably have to find and install a new skin since I believe this one only works with IF. Anyway, I haven't totally made up my mind yet but I'll let y'all know if I decide to convert.