Seam patched version 2.1.0.SP1-NX1 holds a fix for
NXP-12483, that should cover this use case: when there is already a message in the faces context, the "transaction failed" message should not be added on rollback.
This is done by default by the SeamPhaseListener class, holding our patch:
Problem is that this message is still shown in case of rollback because of a "quota exceeded" exception, whereas another error is also visible ("Your content can not be created, the quota of the container /default-domain/workspaces is exceeded.", for instance).