Aha, I figured it out.
When you stretch Sins beyond a certain size, interface elements reorganize themselves. This has unexpectedly just broke my interface mod I've been working on, since I have had it running in 1024x768 mode for testing, not realizing that when the Sins window is expanded, interface elements move. Since the top bar is always, well, on the top, it's not an issue there, but everything on the bottom changes.
Hence the infocard problem. At a high resolution like 1920x1080, the infocard moves from above the right panel of the bottom bar to the very bottom-right of the screen, after which the change on offsetFromBottomBarBottomRight apparently has no effect.
I'll probably shoot off an email to Ironclad regarding this and the other interface issue. Things like this kind of make interface modding beyond simply recoloring and changing alpha channels pointless. The mod I was doing moved the resource counters to the bottom, and it worked at 1024x768 (although anything short of 100% alpha is faded, since the icons and numbers are not rendered on top of the brush) but like I said above, I can no longer make it a standard feature without forcing people to use a resolution from 1998.