Suggested by @MarcoFalke after #14627 and possibly #14420. We should warn if an unrecognised/incorrect section is present in bitcoin.conf. i.e `[testnet]` is present instead of `[test]`.
nMaxConnections = std::max(std::min<int>(nMaxConnections, FD_SETSIZE - nBind - MIN_CORE_FILEDESCRIPTORS - MAX_ADDNODE_CONNECTIONS), 0);
    nFD = RaiseFileDescriptorLimit(nMaxConnections + MIN_CORE_FILEDESCRIPTORS + MAX_ADDNODE_CONNECTIONS);
    if (nFD < MIN_CORE_FILEDESCRIPTORS)
        return InitError(_("Not enough file descriptors available."));
    nMaxConnections = std::min(nFD - MIN_CORE_FILEDESCRIPTORS - MAX_ADDNODE_CONNECTIONS, nMaxConnections);
    if (nMaxConnections < nUserMaxConnections)
        InitWarning(strprintf(_("Reducing -maxconnections from %d to %d, because of system limitations."), nUserMaxConnections, nMaxConnections));
    
    if (gArgs.IsArgSet("-debug")) {
        
        const std::vector<std::string> categories = gArgs.GetArgs("-debug");
        if (std::none_of(categories.begin(), categories.end(),
            [](std::string cat){return cat == "0" || cat == "none";})) {
            for (const auto& cat : categories) {
                if (!g_logger->EnableCategory(cat)) {
                    InitWarning(strprintf(_("Unsupported logging category %s=%s."), "-debug", cat));
                }
            }
        }
    }
    
    for (const std::string& cat : gArgs.GetArgs("-debugexclude")) {
        if (!g_logger->DisableCategory(cat)) {
            InitWarning(strprintf(_("Unsupported logging category %s=%s."), "-debugexclude", cat));
        }
    }
    
    int ratio = std::min<int>(std::max<int>(gArgs.GetArg("-checkmempool", chainparams.DefaultConsistencyChecks() ? 1 : 0), 0), 1000000);
    if (ratio != 0) {
        mempool.setSanityCheck(1.0 / ratio);