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.
if (proxy_arg != "" && proxy_arg != "0") {
        
        if (args.SoftSetBoolArg("-listen", false))
            LogPrintf("%s: parameter interaction: -proxy set -> setting -listen=0\n", __func__);
        
        
        if (args.SoftSetBoolArg("-upnp", false))
            LogPrintf("%s: parameter interaction: -proxy set -> setting -upnp=0\n", __func__);
        if (args.SoftSetBoolArg("-natpmp", false)) {
            LogPrintf("%s: parameter interaction: -proxy set -> setting -natpmp=0\n", __func__);
        }
        
        if (args.SoftSetBoolArg("-discover", false))
            LogPrintf("%s: parameter interaction: -proxy set -> setting -discover=0\n", __func__);
    }
    if (!args.GetBoolArg("-listen", DEFAULT_LISTEN)) {
        
        if (args.SoftSetBoolArg("-upnp", false))
            LogPrintf("%s: parameter interaction: -listen=0 -> setting -upnp=0\n", __func__);
        if (args.SoftSetBoolArg("-natpmp", false)) {
            LogPrintf("%s: parameter interaction: -listen=0 -> setting -natpmp=0\n", __func__);
        }
        if (args.SoftSetBoolArg("-discover", false))
            LogPrintf("%s: parameter interaction: -listen=0 -> setting -discover=0\n", __func__);
        if (args.SoftSetBoolArg("-listenonion", false))
            LogPrintf("%s: parameter interaction: -listen=0 -> setting -listenonion=0\n", __func__);
        if (args.SoftSetBoolArg("-i2pacceptincoming", false)) {
            LogPrintf("%s: parameter interaction: -listen=0 -> setting -i2pacceptincoming=0\n", __func__);
        }
    }