### 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_
true, true);
        if (options.exists("confTarget") && options.exists("conf_target")) {
            throw JSONRPCError(RPC_INVALID_PARAMETER, "confTarget and conf_target options should not both be set. Use conf_target (confTarget is deprecated).");
        }
        auto conf_target = options.exists("confTarget") ? options["confTarget"] : options["conf_target"];
        if (options.exists("replaceable")) {
            coin_control.m_signal_bip125_rbf = options["replaceable"].get_bool();
        }
        SetFeeEstimateMode(*pwallet, coin_control, conf_target, options["estimate_mode"], options["fee_rate"], false);
        
        if (!options["outputs"].isNull()) {
            if (options["outputs"].isArray() && options["outputs"].empty()) {
                throw JSONRPCError(RPC_INVALID_PARAMETER, "Invalid parameter, output argument cannot be an empty array");
            }
            CMutableTransaction tempTx;
            AddOutputs(tempTx, options["outputs"]);
            outputs = tempTx.vout;
        }
        if (options.exists("reduce_output")) {
            reduce_output = options["reduce_output"].getInt<uint32_t>();
        }
    }
    
    
    pwallet->BlockUntilSyncedToCurrentChain();
    LOCK(pwallet->cs_wallet);
    EnsureWalletIsUnlocked(*pwallet);
    std::vector<bilingual_str> errors;
    CAmount old_fee;
    CAmount new_fee;