SF_10.1, SF_10.2, SF_11.0, SF_11.1, SF_11.2, SF_12.0, SF_12.1, SF_12.2, SF_13.0, SF_13.1, SF_13.2, SF_13.3, SF_14.0, SF_14.1, SF_14.2, SF_14.3 - https://docs.sitefinity.com/for-developers-work-with-threads

DeleteThread.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using Telerik.Sitefinity.Services;

namespace Telerik.Sitefinity.Documentation.CodeSnippets.DevGuide.SitefinityEssentials.Modules.Comments.Threads
{
    public partial class ThreadsSnippets
    {
        public void DeleteThread(string threadKey)
        {
            var cs = SystemManager.GetCommentsService();
            cs.DeleteThread(threadKey);
        }
    }
}