The user of-course can already implicitly work out this information from comparing the fee-rate with the actual fee.

I think that it would be useful for people not wanting to do this arithmetic in their head.

{
    QString strHTML;
    LOCK2(cs_main, wallet->cs_wallet);
    strHTML.reserve(4000);
    strHTML += "<html><font face='verdana, arial, helvetica, sans-serif'>";
    int64_t nTime = wtx.GetTxTime();
    CAmount nCredit = wtx.GetCredit(ISMINE_ALL);
    CAmount nDebit = wtx.GetDebit(ISMINE_ALL);