Server default difficulty is 1 (easy), should be 2 (normal)

Can confirm that this issue is still present in 1.16.5 and 21w15a.

Can confirm in 1.18.1.

Here's a code analysis along with a potential fix regarding this issue.

Code Analysis:

The following is based on a decompiled version of Minecraft 1.18.1 using MCP-Reborn.

net.minecraft.server.dedicated.DedicatedServerProperties.java

public class DedicatedServerProperties extends Settings<DedicatedServerProperties> {
   ...
   public final Difficulty difficulty = this.get("difficulty", dispatchNumberOrString(Difficulty::byId, Difficulty::byName), Difficulty::getKey, Difficulty.EASY);
   ...

If we look at the above class, we can see that by default, servers have their difficulty set to EASY.

Potential Fix:

Simply changing the appropriate line of code to set the default server difficulty to NORMAL, should resolve this problem. The correct line of code within its class should look something like the following:

net.minecraft.server.dedicated.DedicatedServerProperties.java

public class DedicatedServerProperties extends Settings<DedicatedServerProperties> {
   ...
   public final Difficulty difficulty = this.get("difficulty", dispatchNumberOrString(Difficulty::byId, Difficulty::byName), Difficulty::getKey, Difficulty.NORMAL);
   ...

Can confirm in 1.19.

Can confirm in 1.19.2.