Firstly, I suggest you actually read the MCard Terms. Not just 4.6, but all of them. They are very clear about who/what MCard is, and 14.6 makes complete sense once this is acknowledged:
In other words, "MCard" is a retailer, and not the medium on which the ticket is held.
The condition applicable to the day ticket is no less clear than any other condition on tickets.
That leads to interpretation. I think this argument built out of the structure of Clause 14 of NRCOT is back to front. The condition of travel is engaged when buying the MCard ticket. That condition in clause 4.6 of the MCard T&Cs is
explicitly that you need to buy the other half of a split from the last station in the West Yorkshire area that your train stops at. It doesn't talk to the wider rules of split ticketing because it doesn't need to - it defines a specific provision for how it may be used.
@Starmill demonstrates this. The focus on Section 14 rights due to the operation of 14.2 and 14.3 is blinding people to the plain english meaning of 14.1, which doesn't say anything about the number of tickets per journey, whether 1, 2 or 100. To repeat, the clause is very simple - "Some Tickets specifically exclude their use in conjunction with other Tickets. This will be made clear in the terms and conditions when buying such Tickets".
I don't disagree. But if we're taking such a rigorous view of conditions, surely that requires that every purchaser, of every ticket, is expressly advised of every condition, every time they purchase them - not just MCard 4.6, but anything that may be relevant. We're expected to be able, as responsible adults, check the conditions that apply to our purchases - and this information is straightforwardly available.
I'd rather that 14.1 wasn't there, and I'd rather that WYCTL didn't apply that condition. But I struggle to understand how there can be opposition as a matter of law, rather than as consumer and political (for those in the relevant area) protest.
. Funny how many people see the world in that way.