I edited a question with the following intension:
remove the noise at the beginning which is not related to the actual question at all:
Many questions have been asked about how to find my Pi on my network.
This is a statement that says nothing. Many questions have also been asked about running Python. So what?
In addition this statement has provoked an answer that is about identifying Pis which is not what the OP wants, as he stated in the comments to that answer:
Perhaps my initial description was not clear enough. I'm not particularly looking for a way of identifying the Pi's. I already have that covered. What I'm looking for is to run one or more bash commands by altering the /boot/cmdline.txt file. This all without the need of logging in via ssh - even once.
rephrase to make the point clear
Others - including myself - have time consuming issues while trying to deploy a batch of fresh Pi's.
So what he's really doing is deploying a set of RPis. Therefore I simplified to
I'm trying to deploy a batch of fresh Pis, [...]
make the background of the question understandable:
Some people have tried to identify Pis. Why? Because when you flash an image, all Pis are the same. But you don't want them to. IP conflicts are bad etc.
How does that relate to OP's problem? Making a Pi uniquely identifyable is very similar to what the OP wants: deploying a batch of Pis.
Next we have 4 statements: a) when you deploy a batch of Pis and b) your question title is
Use /boot/cmdline.txt for creating first-boot script
and c) your task is similar to making Pis identifiable and d) you're saying that
While the creation of custom images could be a solution for these issues
then each of these custom images is individual (or "unique").
Therefore I wrote the sentence like this:
The creation of custom images for each individual Pi could be a solution for these issues
highlight the differences:
OP gave the statement
With (only) the /boot directory open for access on regular machines (Win/OSX)
which clearly indicates that he does not want individual images but the same image for all Pis.
Therefor I highlighted the difference here:
I'm wondering if there are easier solutions that involve a common image for all Pis
emphasize the only option left:
IMHO the original question sees 3 possible solutions:
a) boot the Pi and modify it then. Obvious, but involves lot of effort: insert SD, boot, open terminal, execute command, ... So that's not what OP wants.
b) Modify the IMG file before flashing ("custom images"). Also involves a lot of effort: boot a Linux machine, mount the image, perhaps even resize partition, modify file, unmount, ...
cmdline.txt: same IMG for each Pi of the batch, write to SD card, then modify the file, since it is easily editable.
With all the knowledge before, OP does not want all Pis to be the same, so I edited this to be an "individual" text:
[...] to pipe an individual text to a bash script [...]
Conclusion: I spent some effort understanding what OP wants, reading the title, the question, the answers and the comments. I noticed that I didn't get the correct intention reading the question the first time, so IMHO I edited in the sense of the OP.
I agree that this edit cannot be understood from the review queue. I know what the review queue looks like, because I have 10k+ on Stack Overflow. Without opening the question and getting all the context, it's very hard to understand why I made that edit and it may look like vandalism.
As you can see from the long text above, it would never have fit into the comment I could give as the reason for the review. Maybe there's a better short reason than mine.
Another thing which could have contributed: the edit was rejected by moderator Ghanima. Short time before I edited the question, Ghanima first mentioned OP's question and later closed my question as duplicate. Of course that is the reason why I found the question I edited.
To Ghanima, it may have looked like I'm trying to edit another person's question to get an answer to my question, which really is an exact duplicate considering all the above. And no, I didn't do that to help myself, I did it for the sake of OP to get better answers (and has not accepted one yet).