### Is there an existing issue for this?

- [X] I have searched the existing issues

### Current behaviour

See inline discussion at https://github.com/bitcoin/bitcoin/pull/26467#discussion_r1269177446

@whitslack:

> Consider the case where I am paying someone on chain under the stipulation that _they_ will eat the mining fee. (Thus, I specify _their_ address in `subtractfeefrom` when I'm constructing my transaction.) Later, they tell me that they can't wait for confirmation any longer and need an urgent fee bump. If I naïvely specify their output as the `reduce_output`, I may end up paying them _**much more**_ than I intended to if I only have large UTxOs in my wallet.


### Expected behaviour

Not sure.

Improving the docs is one option, but this behaviour seem quite counter intuitive.

My own suggestion:

> Should we disable the adding of new inputs when `reduce_output` is set? If someone really intends to do that, they should probably use `outputs`.

### Steps to reproduce

Haven't tried.

### Relevant log output

_No response_

### How did you obtain Bitcoin Core

Compiled from source

### What version of Bitcoin Core are you using?

Master after #26467

### Operating system and version

Any

### Machine specifications

_No response_
constexpr int RANDOM_CHANGE_POSITION = -1;
    auto res = CreateTransaction(wallet, recipients, RANDOM_CHANGE_POSITION, coin_control, true);
    if (!res) {
        throw JSONRPCError(RPC_WALLET_INSUFFICIENT_FUNDS, util::ErrorString(res).original);
    }
    const CTransactionRef& tx = res->tx;
    wallet.CommitTransaction(tx, std::move(map_value), {});
    if (verbose) {
        UniValue entry(UniValue::VOBJ);
        entry.pushKV("txid", tx->GetHash().GetHex());
        entry.pushKV("fee_reason", StringForFeeReason(res->fee_calc.reason));
        return entry;
    }
    return tx->GetHash().GetHex();
}
/**
 * Update coin control with fee estimation based on the given parameters
 *
 * @param[in]     wallet            Wallet reference
 * @param[in,out] cc                Coin control to be updated
 * @param[in]     conf_target       UniValue integer; confirmation target in blocks, values between 1 and 1008 are valid per policy/fees.h;
 * @param[in]     estimate_mode     UniValue string; fee estimation mode, valid values are "unset", "economical" or "conservative";
 * @param[in]     fee_rate          UniValue real; fee rate in sat/vB;
 *                                      if present, both conf_target and estimate_mode must either be null, or "unset"
 * @param[in]     override_min_fee  bool; whether to set fOverrideFeeRate to true to disable minimum fee rate checks and instead
 *                                      verify only that fee_rate is greater than 0
 * @throws a JSONRPCError if conf_target, estimate_mode, or fee_rate contain invalid values or are in conflict
 */
static void SetFeeEstimateMode(const CWallet& wallet, CCoinControl& cc, const UniValue& conf_target, const UniValue& estimate_mode, const UniValue& fee_rate, bool override_min_fee)