If our BtcFn-Node receives in fact such payment to this address, then they will act as the payer says basing on reading the label;
The label is not public. You can't easily pass messages via Bitcoin.
The idea is OK. I would have just used plain text instead of HTML. Bitcoin sends blocks in chunks of 500 -- splitting in chunks of 10 seems excessive. I don't like having to convince someone in the system to pull data from me.