John, 
I can now see the behaviour your are refering to. However I do not
yet fully understand it. Using your email script I get:


SENDMAILDEBUG=1 PYTHONPATH="$PWD" python 
roundup/scripts/roundup_mailgw.py demo < email_1
tx_SourceCheckAudit(None) pre db.tx_Source: email, nonce: 
35cac65328bed1477b21
tx_SourceCheckAudit(None) post db.tx_Source: email, nonce 
35cac65328bed1477b21
tx_SourceCheckAudit(1) pre db.tx_Source: email, nonce: 
cdc748bdd843bd708bbc
tx_SourceCheckAudit(1) post db.tx_Source: email, nonce 
cdc748bdd843bd708bbc
tx_SourceCheckReact(1) pre db.tx_Source: email, recorded: arrived via: email 
cdc748bdd843bd708bbc
tx_SourceCheckReact(1) post db.tx_Source: email, recorded: arrived via: email 
cdc748bdd843bd708bbc

The history will only mark the changes done to the "issue" object,
I wonder if there is a mixup between the values of tx_Source
for "issue" and "msg" somehow in the way how this is implemented.
Just an idea. My next step is trying to understand how this all
is supposed to work.