using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Text.RegularExpressions;
 
public class Test
{
	public static void Main()
	{
		var tststr = @"Hi I am normal text <strong>but bold</strong> and normal again";
		var lst = new List<string>();
		var former_idx = 0;
		for (var m = Regex.Match(tststr, @"(?s)\s*<(\w+)\b[^>]*>.*?</\1>\s*"); m.Success; m = m.NextMatch())
		{
		    lst.Add(tststr.Substring(former_idx, m.Index - former_idx));
		    lst.Add(m.Value);
		    former_idx = m.Index + m.Value.Length;
		}
		if (former_idx < tststr.Length)
		    lst.Add(tststr.Substring(former_idx, tststr.Length - former_idx));
        Console.WriteLine(string.Join("\n", lst));
	}
}

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