It looks like hovering is out of the question when a macro is running,
but while this macro is running a cell's comment becomes visible when
it is made the active cell and invisible when you deactivate it by
clicking elsewhere. I was even able to add a comment to a cell while
the macro was running. Interestingly the user name that always
prefaces a comment was not there when I added the comment while the
macro was running...

Public Sub Hover_Test()
Dim K As Long, strAddress As String
Do While K < 100000
Range("H1").Value = K
K = K + 1
strAddress = ActiveCell.Address
DoEvents
On Error Resume Next
If ActiveCell.Address < strAddress Then
Range(strAddress).Comment.Visible = False
Else: ActiveCell.Comment.Visible = True
strAddress = ActiveCell.Address
End If
Loop
End Sub

Ken Johnson