Right now this behavior is the default for myfaces core (because this is done on shared).
For be more specific:
The same applies with layout="table"
If something changes for t:messages, h:messages changes too.
But reading the documentation of h:message and h:messages, it seems that there is no reference about how this should be done.
If a change is done here to do this as RI does, the actual applications using myfaces changes too (css style fixes could be needed). But it seems that the right way to do this is something like this:
But I'm not sure about do this. Suggestions?