Calculations/Evaluations are not part of the lightweight template engine NodeBB uses. (AFAIK)
I guess the best would be to intercept the filter:post.getPosts hook and add your custom index values...
Some plugins don't seem to be able to update via the ACP. Doesn't seem to be exclusive to particular plugins, but an array of them can't seem to update on different sites on different distributions that I have running.
I see he same issue as @Technowix was just going to report. Plugins that are upgradable for me seem to want to downgrade to previous version.