It does matter when you claim you have a mandate when in fact, more people wanted the other person.
> when in fact, more people wanted the other person
The whole point of the comment you replied to was that you don't know that - can't know that. People voted under the current system, we don't know what their voting behavior would have been if the voting system would have been based on popular votes! For example, those in states where the winner was always clear from the start might have gone voting instead of staying at home, or they might not have voted for a 3rd party. It's not like the popular vote is 70%/30%, the total difference is far less than a single percentage point.And Trump does have a mandate. The system is at it is - it has been like that since the very beginning of this country. I may not agree personally, but he won, and I really don't see any positive point in attempts that try to reinterpret the result. Remember, some day the roles may be switched.
If anything, I think the current system suppresses the vote. I'm in a red state so my vote never counts.
Obviously it's too late for any change to the electoral college to affect this election. But we could know this in the future. You make what you measure and we're measuring the wrong thing.