I think you will need to modify pages/posts.ascx.cs as below (just commenting out the code in the else branch) and then recompile.
FWIW I also don't like the post jumping functionality and have removed it from my installation using this approach.
if (findMessageId > 0)
{
this.Pager.CurrentPageIndex = rowList.First().Field(columnName: "PageIndex");
// move to this message on load...
if (!this.PageContext.IsCrawler)
{
PageContext.PageElements.RegisterJsBlockStartup(
this, "GotoAnchorJs", JavaScriptBlocks.LoadGotoAnchor("post{0}".FormatWith(findMessageId)));
}
}
else
{
// move to this message on load...
//if (!this.PageContext.IsCrawler)
//{
// PageContext.PageElements.RegisterJsBlockStartup(
// this,
// "GotoAnchorJs",
// JavaScriptBlocks.LoadGotoAnchor("post{0}".FormatWith(rowList.First().Field(columnName: "MessageID"))));
//}
}