At any hearing, any party of record shall be entitled to enter his or her appearance, introduce evidence, examine and cross-examine witnesses, make arguments and generally participate in the conduct of the proceeding. Appearances shall be entered either in writing or, at the discretion of the Commission, upon the record of the hearing. If appearance in writing is filed, a copy thereof shall be delivered, or mailed postage prepaid, to all other parties to the proceeding by the filing party.
18- 185 C.M.R. ch. 110, § 12