IrcTwitch with clean code solution to the compiler check dillema. Also allows you to neatly check the feature availability in v2.0 in run time!

IrcTwitch.cs

using System;
using System.Diagnostics;
using System.Linq;

namespace HotBot.Core
{
	public class TwitchIrc
	{
		//Imagine this class is only available when !SOME_CONSTANT
	}

	internal class TwitchIrcFactory
	{
		private static bool _verified = false;
		private static bool _featureAvailable = false;

		public static bool FeatureAvailable
		{
			get
			{
				if (!_verified)
				{
					_verified = true;
					TryEnableFeature();
				}
				return _featureAvailable;
			}
		}

		[Conditional("FEATURE_TWITCH_IRC")]
		private static void TryEnableFeature()
		{
			_featureAvailable = true;
		}

		//requires System.Diagnostics
		//Since you cant use ! for the statement; instead have a constant that declares the feature is supported for the platform being targetted by the build

		public static TwitchIrc Create(/*arguments you need to construct an instance of TwitchIrc, but figured there werent any*/)
		{
			if (FeatureAvailable)
			{
				return new TwitchIrc();
			}
			else
			{
			}
			//Also i said static because you seem not to have issues with the singleton anti-pattern
			return new TwitchIrc();
		}

		public static void Example_Before()
		{
#if SOME_CONSTANT
			//Every single time you need this shit in order to be compiler safe
			//Not only does it break tabs
			//but also if you ever do figure out how to use it on win 10 apps (getting theoretical)
			//then you need to modify all the code
			//Also this is for just one feature being controlled by 1 constant
			//What if that starts to expand?+
			var irc = new TwitchIRC();
#endif
		}

		public static void Example_After()
		{
			var irc = TwitchIrcFactory.Create();
			if (irc == null)
			{
				return;
			}
			//SAFE TO USE IRC
		}
	}

	///////////////////////////////////
	/////////////////////////////////// PERSONAL FLAVOUR TO THE PATTERN USING PRIVATE CONSTRUCTOR AND NESTED CLASSES
	///////////////////////////////////

	public class TwitchIrc2
	{
		private TwitchIrc2()
		{
		}

		public static class Factory
		{
			private static bool _verified = false;
			private static bool _featureAvailable = false;

			public static bool FeatureAvailable
			{
				get
				{
					if (!_verified)
					{
						_verified = true;
						TryEnableFeature();
					}
					return _featureAvailable;
				}
			}

			[Conditional("FEATURE_TWITCH_IRC")]
			private static void TryEnableFeature()
			{
				_featureAvailable = true;
			}

			public static TwitchIrc2 CreateInstance()
			{
				if (FeatureAvailable)
				{
					return new TwitchIrc2();
				}
				else
				{
				}
				return new TwitchIrc2();
			}
		}

		public static void Example_After()
		{
			if (TwitchIrc2.Factory.FeatureAvailable)
			{
				//Grey out some UI and enable tool tip notifying the platform not supporting the feature
			}
			else
			{
				//Enable that shit
				var irc = TwitchIrc2.Factory.CreateInstance();
			}
		}
	}
}