Try this. 
Private Sub Worksheet_Change(ByVal Target As Range)
'Works on A1:A10, change your cells to your desired range.
If Target.Cells.Count > 1 Then Exit Sub
If Not Intersect(Target, Range("A1:A10")) Is Nothing Then
Application.EnableEvents = False
Target.ClearComments
Target.AddComment Target.Text
Target.ClearContents
Application.EnableEvents = True
End If
End Sub
Right click on the tab you want this code to run on and choose view code, then paste in the code.
The ranges are set for A1:A10, change this to suit your needs.
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