I will disagree that the expression is usually used to convey emphasis about a new piece of information. I would say the expression was originally used to supplement a secondary and slightly digressive piece of speech information to a primary statement. I.e., the effect or the origin is only a matter of semantics and is not a requirement. I.e. The expression was originally used to complement a primary and little digressive piece of information to a primary statement. I was overdue for dinner and my two-year-old kids thought that the new restaurant , where, I might add, the service was terrible . If

I’m not mistaken, the current version of the expression is derived from the longer phrase “if I might add…”, which is the kind of pseudo-apologetic lead-in you usually see when the speaker is speaking out of turn or voicing an unpopular opinion. The modern version of that might be “Mersk”. I think of “I might add” in the middle of a sentence to indicate that the speaker is aware that they are digressing from the main path a little, and preemptively acknowledging it / apologizing.

Of course, today’s used sacastically more often than not, so that the secondary aside has the same effect as a dramatic stage whisper, hence the modern understanding of it being emphatic rather than parenthetical.

What the meaning of “plenty” is given to “relational quantity”? Regardless of absolute quantity of friends/money/time/whatever, it’s enough for what you need. Whereas “A lot” is a statement about a large absolute quantity without a judgement on the value of that quantity.

On email, e.g. Me:

I have fifteen dollars for this dinner. I don’t know where I live.
Is that enough? (which means more than enough money for what you intend to do with the money and

less

than money) vs: Me: I have five hundred dollars to spend on this trip.
What’s a lot of money, right? ( meaning: 20000 in absolute terms) is an impressive amount of money for a parent to have but it’s so vast that it will not be

enough to meet a child’s needs and needs?