This one was interesting!
I could not get the inserted  cells or row  to 'set' or 'clear' the formatting
no matter what I did.
Programatically used after inserting  row (or Cells):

Selection.Font.Bold = False
Selection.Font.FontStyle = "Regular"

I wonder if there is a 'seeting' that needs to be 'turned off' that defaults
the cell  formatting to the neighboring or inserted cells? Oh well. What DID
solve the issue by placing a 'value' into the inserted cells, then formatting
them to 'regular' font:

Sub insertrow()
iColumns = ActiveCell.CurrentRegion.Columns.Count
Range(ActiveCell, ActiveCell.Offset(0, iColumns - 1)).Select
Selection.Insert Shift:=xlDown
Selection.Value = "x"
Selection.Font.FontStyle = "Regular"
End Sub