Try:
Sub DemoA()
Dim StrCmnt As String, ArrAuth, i As Long, j As Long, k As Long
StrCmnt = vbCr: ArrAuth = Array("Author1", "Author2", "Author3")
With ActiveDocument
For i = LBound(ArrAuth) To UBound(ArrAuth)
k = 0
For j = 1 To .Comments.Count
With .Comments(j)
If .Author = ArrAuth(i) Then k = k + 1
End With
Next
StrCmnt = StrCmnt & vbCr & ArrAuth(i) & " - " & k
Next
End With
MsgBox "Comment Count by Designated Author:" & StrCmnt
End Sub
and:
Sub DemoB()
Dim StrCmnt As String, StrRevn As String, i As Long
StrCmnt = vbCr: StrRevn = vbCr
With ActiveDocument
For i = 1 To .Comments.Count
With .Comments(i)
If .Author <> "" Then
If InStr(StrCmnt, vbCr & .Author & vbCr) = 0 Then
StrCmnt = StrCmnt & .Author & vbCr
End If
End If
End With
Next
For i = 1 To .Revisions.Count
With .Revisions(i)
If .Author <> "" Then
If InStr(StrRevn, vbCr & .Author & vbCr) = 0 Then
StrRevn = StrRevn & .Author & vbCr
End If
End If
End With
Next
End With
MsgBox "Comment Authors:" & StrCmnt
MsgBox "Revision Authors:" & StrRevn
End Sub