EDITED 2019-02-08

`maxTxFee` is a global variable, used by both the raw transaction and wallet RPCs. It's set from `-maxtxfee`.

~listed in the global help text in init.cpp, but is only set in `WalletInit::ParameterInteraction()`. If the wallet is disabled, then `-maxtxfee` is ignored and the default is used.~

~This behaviour has existed since the mempool was changed to limit acceptance based on `maxTxFee` in https://github.com/bitcoin/bitcoin/commit/fa331db68bcc68e4c93fb45aaa30f911b0ecfe1a.~

~Short-term fix is to move the `-maxtxfee` handling to `InitParameterInteraction()` in init.cpp.~
EDIT: `maxTxFee` initiation bug fixed in #15357 

I don't think we should share this setting between the node and wallet.
{
    if (gArgs.IsArgSet("-walletdir")) {
        fs::path wallet_dir = gArgs.GetArg("-walletdir", "");
        boost::system::error_code error;
        
        fs::path canonical_wallet_dir = fs::canonical(wallet_dir, error);
        if (error || !fs::exists(wallet_dir)) {
            return InitError(strprintf(_("Specified -walletdir \"%s\" does not exist"), wallet_dir.string()));
        } else if (!fs::is_directory(wallet_dir)) {
            return InitError(strprintf(_("Specified -walletdir \"%s\" is not a directory"), wallet_dir.string()));
        
        } else if (!wallet_dir.is_absolute()) {
            return InitError(strprintf(_("Specified -walletdir \"%s\" is a relative path"), wallet_dir.string()));
        }
        gArgs.ForceSetArg("-walletdir", canonical_wallet_dir.string());
    }
    LogPrintf("Using wallet directory %s\n", GetWalletDir().string());
    uiInterface.InitMessage(_("Verifying wallet(s)..."));
    
    
    
    bool salvage_wallet = gArgs.GetBoolArg("-salvagewallet", false) && wallet_files.size() <= 1;
    
    std::set<fs::path> wallet_paths;
    for (const auto& wallet_file : wallet_files) {
        WalletLocation location(wallet_file);
        if (!wallet_paths.insert(location.GetPath()).second) {
            return InitError(strprintf(_("Error loading wallet %s. Duplicate -wallet filename specified."), wallet_file));
        }