Sorry I probably should have pinged you; irssi-plugin-xmpp had the same issue, see #817171, and I fixed it by making use of DEB_HOST_MULTIARCH and specifying an explicit module path, see https://anonscm.debian.org/cgit/collab-maint/irssi-plugin-xmpp.git/commit/?id=542ef1528821ffc0b048b38bb431918fcf02203f
Besides, irssi-plugin-otr needs to be rebuild anyways because we've had an upload of a new major version of irssi, and since there has been some ABI breakage in the past, the irssi folks introduced ABI versioning and won't load anything that wasn't compiled against the same ABI version (no change required, just a rebuild) Florian