On my Linux Mint 19.1:
```bash
$ umask
0022
```

After the first run of `bitcoin-qt -sysperm=false` the `0700` permissions are expected for both the datadir (`~/.bitcoin`) and the walletdir (`~/.bitcoin/wallets`).

Actually, the directories are created with such access permissions:
```bash
$ stat ~/.bitcoin | grep Uid
Access: (0755/drwxr-xr-x)  Uid: ( 1000/ hebasto)   Gid: ( 1000/ hebasto)
$ stat ~/.bitcoin/wallets | grep Uid
Access: (0755/drwxr-xr-x)  Uid: ( 1000/ hebasto)   Gid: ( 1000/ hebasto)
```

Refs:
- #4286
- #13371
- #13389

NOTE: reading through the initial PR #4286 makes me think it was controversial. Is it a better and simpler way to just get rid of `-sysperm` option? I believe a user who needs this option can easily run `chown` command.
nMaxConnections = std::max(std::min<int>(nMaxConnections, fd_max - nBind - MIN_CORE_FILEDESCRIPTORS - MAX_ADDNODE_CONNECTIONS - NUM_FDS_MESSAGE_CAPTURE), 0);
    if (nFD < MIN_CORE_FILEDESCRIPTORS)
        return InitError(_("Not enough file descriptors available."));
    nMaxConnections = std::min(nFD - MIN_CORE_FILEDESCRIPTORS - MAX_ADDNODE_CONNECTIONS - NUM_FDS_MESSAGE_CAPTURE, nMaxConnections);
    if (nMaxConnections < nUserMaxConnections)
        InitWarning(strprintf(_("Reducing -maxconnections from %d to %d, because of system limitations."), nUserMaxConnections, nMaxConnections));
    
    init::SetLoggingCategories(args);
    init::SetLoggingLevel(args);
    
    int64_t nPruneArg = args.GetIntArg("-prune", 0);
    if (nPruneArg < 0) {
        return InitError(_("Prune cannot be configured with a negative value."));
    }
    nPruneTarget = (uint64_t) nPruneArg * 1024 * 1024;
    if (nPruneArg == 1) {  
        nPruneTarget = std::numeric_limits<uint64_t>::max();
        fPruneMode = true;
    } else if (nPruneTarget) {
        if (nPruneTarget < MIN_DISK_SPACE_FOR_BLOCK_FILES) {
            return InitError(strprintf(_("Prune configured below the minimum of %d MiB.  Please use a higher number."), MIN_DISK_SPACE_FOR_BLOCK_FILES  1024  1024));
        }
        fPruneMode = true;
    }
    nConnectTimeout = args.GetIntArg("-timeout", DEFAULT_CONNECT_TIMEOUT);
    if (nConnectTimeout <= 0) {
        nConnectTimeout = DEFAULT_CONNECT_TIMEOUT;
    }