Of course each case has to be tried on its own facts and merits based on the particular circumstances, but until there is absolute certainty on the matter in the form of an amendment to the relevant legislation to specifically cater for signatures of land sale agreements in this manner, or a Supreme Court of Appeal ruling confirming this stance, we strongly advise against signing any agreement for the alienation of land other than by way of the traditional wet ink on paper.
When we have any documentation commissioned, we essentially swear, by providing proper identification, before someone who has the authority to administer an oath (such as a police official, an attorney, a charted accountant, etc.), that we understand the content of the documentation and find it binding on our conscience. The commissioner confirms this by placing his/her signature and stamp. Usually this is a process done face to face but with these unprecedented times of living in lockdown and trying to reduce the spread of infection, it may be wise to consider alternative means of commissioning.