@Riemann 's avatar isn’t HAL’s “eye”, though there is rather a resemblance there, and it is a lens of sorts. It’s an Einstein ring, from a distant galaxy’s light being bent by the gravity of a closer object.
And “Hal” is most often for “Henry”, not “Harold”, as fans of Shakespeare might know. Though it might also be used for Harold.
I typically post from my phone, so I’ve never seen their avatar as anything more than a tiny thumbnail. And for years now I’ve assumed it was HAL.
And now I look up HAL’s eye and realize it looks so utterly different that even in thumbnail form I shouldn’t have confused it.
Ignorance fought!
Huh. I’ve never zoomed in on that, always thought it was a camera lens.
Molly and Sally I don’t mind. Their transformation to given names in their own right happened long enough ago that they’re not often used as diminutives for the original names any more. Peggy, I’m on the fence about (not many Margarets about these days, particularly in the UK). Hal would annoy me, but maybe only because I know my Shakespeare. 
OB
It’s not a law, but it is a societal convention, so I suspect it would be harder to go the other direction. Have you ever heard anyone say “My name is Alex, but I go by Alexander”? I would be easier just to have a completely unrelated nickname.
Though even that is fraught, since it’s generally frowned upon to come up with your own nickname if it’s not related to your existing name.
So I totally get what they’re saying. My counterargument is just that, in many circumstances, they would be forced to use the longer name. It will be likely used in school by teachers, and on official forms, and prescriptions, and so on.
I can see how someone who has gone by a nickname all their life but has to use this weird name officially might want to dispense with all of that for their kid. Plus, they may just generally not like the longer name. And, ultimately, naming kids is done based on the parents’ preferences. Most cultures don’t consult with the kid.
Yes! And people will go by what their freinds call them rather than their real name.
Camo, as in the hunting apparel, is really Cameron, never hear anyone call him Cameron even his parents. Several people named after their fathers who go by Junior. No one thinks of them by the father’s name, they are Junior. A couple of 3rd generation names who don’t go by James Whatever III, just Trey. Two guys who are simply T. One references his first name, the other his last name, everyone just calls them T. Most people would not even know the real names of Camo, Junior, Trey, or T.
Point taken.
However, in those contexts, perhaps it is better to have an easily reconciled solution, such as a given name that is default, or, in the parlance of our tames, “is jake!”?
I happen to be named John, and, as correctly said above, it has only a bare connection to the other name Jonathan (or alternate spellings). Different name entirely, and, yes, some people do try to make some back-formed abomination as though it were somehow “fancier” to use the longer (but wrong) name. I very quickly correct them.
However, as to the OP, I also find it cringeworthy to hear or see things like “Jack” used as official first names. That happens to be a nickname some of my family use, or some friends who are trying to annoy me, but…
it isn’t “wrong”…but it is “cringe”…to have that as an official given name.
It seems affected, in a special kind of way that I find offensive. Perhaps in that I use some of those nicknames to differentiate people I know, or in that I sometimes have one used on me. It wouldn’t occur to me that that should be a proper name, and it diminishes the uses I have for these nicknames (“Hal,” “Bill,” whatever…the specific cases don’t matter).
An excessively fancy affectation, and I don’t like it.
“Meghan” is a pseudo-Irish misspelling of “Megan,” which is a diminutive of “Meg,” which is a short form of “Margaret.” So in one particular part of the OP, you are misdirecting your ire.
Now explain that to every single person I interact without outside my immediate family.
I’m well aware my ire is irrational and not necessarily consistently directed. As with Sally and Molly, I think Megan is now sufficiently detached from Margaret that I’m fine with it being a given name in its own right.
OB
To me, it is something so inconsequential that not only would I not give it a second thought, I would rarely even give it a first. Is this a generational thing, as culture is tending in the direction of less formality in general?
You don’t call him Eddie Baby, do you, sweetie?
Ditto.
The names that don’t bother the OP, such as Sally for Sarah, had to have gotten that way somehow. So it’s fine as long as he wasn’t around when it happened? I have no problem whatsoever with naming a kid Alex, Jack, Max, etc.
No, but I have heard people say “My name id Alexander”.
Yes, but “Meg” is not short for “Megan.” “Megan” is a nickname for “Meg.”
I know someone like that, too. I was a coauthor on her first academic paper where she had “Jenny T. Smith” down as her name. I commented she should be sure to put her “official” name, so all of her publications would properly link to her. She said Jenny was her official name, and what was on her birth certificate
I’m generally known by a shortened version of my name, so on papers I frequently have to correct it to the full version, and the correct of several alternative spellings.
My own name is an ad hoc shortening of an Italian name. I often just give the Italian version when ordering food, because it’s familiar enough that people don’t screw it up. People hearing or reading my actual name just correct it to whatever version they find more appealing/ familiar.
Are you thinking particularly about a couple who named their children Archie (instead of Archibald) and Lilibet (instead of Elizabeth)?
This just seems like yet another case of resistance to change; trying to preserve things the way they are now (or used to be in some golden era), ignorant of the fact that any such golden era was itself arrived at by a process of change, and also contained people complaining that things aren’t what they used to be.
It’s probably not a great idea to name your kid in some way that is going to subject them to daily inconvenience or ridicule (of course there are those that would argue that such things build character), but to pretend there is some list of ‘right names’ is just weird gatekeeping.
Can I guess how you feel about the plague of Liams we seem to have been infested with in recent years?