Reading through, appears this is mostly a manufacturing concern that goes away once the chip is actually active. Correct? The charge buildup goes away, and then there's no further need for the diode antenna.

However, second question, does any chip actually use these for anything afterward? Or are these ever built so they actually do something other than simple provide manufacturing protection?

Example, they build up charge. So then the charge build up itself is effectively used as some form of remote communication method or channel between various portions of the chip. The diode discharges and in discharging effectively acts as some form of communication transfer.

Others, or it serves multiple purposes. One during manufacturing, one after manufacturing? Safety mechanism during manufacturing, and then the charge buildup location is oscillated, purposely charged, or used as a charge outlet for some other reason?

Others, Light Emitting Diode is, kind of by the name, a diode. Any of these that basically do blinking communication or something similar? Emits light when the charge breaks down, then that is picked up and used as data transfer?

Others, not going into extensively. Tune radio and TV receivers (varactor diodes). Generate radio-frequency oscillations (like actual antennas) (tunnel diodes, Gunn diodes, IMPATT diodes).

Basically, anything other than a safety mechanism for manufacturing?

You're correct that these are for manufacturing only. I've never heard of them being used for actual design purposes and that's probably because if you wanted an actual diode, you'd just use a "real" one.