I don’t recall ever seeing a discussion or decision to remove numbers from titles, and I would strongly object to it. I am not sure what Matthew is saying since he says you can add it to the Nickname field which is the only place it would appear anyways.
It is absolutely standard practice to attempt to add numbers to titles. It is a way of clearly differentiating individuals and for showing lines of succession. Can you name any lineage or peerage book which doesn’t follow this practice? Even one?
This does occasionally cause some disagreements when there are different ways of numbering. Titles occasionally become extinct and are later re-created, bringing up the question of do you start over the numbering for each creation? I generally do not. It defeats the purpose of clearly differentiating different holders of the title.
When there is a disagreement about numbering, I think there is an absolute gold standard which should be followed, and that’s Complete Peerage. It has long been held as the authority on the peerage of England, even with the occasional additions and corrections over the years.
To make a decision to not use numbers for titles at all just because it is not always clear cut is to throw the baby out with the bath water. It makes no sense. It is also not standard genealogical practice, and would put wikitree once again out of step with what are norms everywhere else in the world.
With specific regard to the Earldom of Leicester, I think Richardson has made a mistake and gone off with his own numbering system different from standard practice. This was extremely early in the development of the peerage, and what you were was not so much what you were called, it was what you held. The father of Robert of Meulan was one of the richest and powerful men of his time. The contemporary chronicler Orderic Vitalis states, that when he was granted the town of Leicester by the King he was held to have become the Earl of Leicester. This is where Complete Peerage starts their numbering, it’s where wikitree should start its numbering, and Richardson is incorrect to start his numbering with his son. If there is some minor disagreement over this, it is a perfect example of why we use Complete Peerage as the Gold Standard. (see Complete Peerage, vol. 7 p. 523-525 for a complete discussion).