Realistically, no. But should as in recommended, yes.

If I read your username I’m going to read/say it in my head, so I’m going to attempt to pronounce it.

If every username was just a long number, I’d probably start to find a pronounceable, and specifically memorable substring to remember. A username of “846768556888434”, I’ll call you “34” from now on.

In the case of OP, “YICHM”, you’ll probably just be called “Y-CHIM” or maybe “Why Jim”. Is that your name? No. But is that what I’ll remember, probably.

But even pronounceable names, like mine, probably get shortened. Just “Mimic” or just “Jar”.

Which is all just to say I’m going to try and pronounce it no matter what you have for a username, so if you want others to pronounce it the same way, it should be pronounceable.

a shitty website

Or worse a PDF of the menu.

Additionally if the phrase mom/dad already failed to get their attention, or if I’m in a location with many other moms/dads.

Because he agrees with whomever he spoke to last. If you talk to him more, he agrees with you more.