Warsaw Will,
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I'm not in the habit of saying things that I don't know, or at least feel strongly, are true, even if social pressure attempts to coerce me by suggesting I'd better do the polite thing. I urge others to resist that subservience as well. You didn't seem 'sorry', in your initial replies, and this was confirmed in your last reply. It is pretty clear you felt no real regret in informing me that your opinion on the matter is at odds with mine. It is no more genuinely considerate to announce a difference in opinion with 'I'm sorry' or 'I regret to inform you', than is to send a 'With deepest sympathies' card to someone on their birthday....it is a false echo of consideration that no one believes is genuine. I commend you for dropping the niceties. Honesty is the best policy.
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Are you thoroughly convinced that everything in existence, or more precisely anything that could properly exist is certain to be found on the internet?
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Even if you are...you are wrong about "It and I are me/I" appearing nowhere on the internet. You, yourself have now added it several times. What does that suggest about the value of that metric?
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You analogy, that attempts to restrict the possibilities of what a name or a pronoun might describe in the rigid way addition of integers is restricted, falls flat. Spoken language is far more nuanced than simple addition.
"1+1+1+1-3=1" is the same no matter how it is read.
"You don't think she wants me to go to that store with you, do you?" does not simply have one absolute meaning.
Analogies are powerful tools. As with any powerful tool, it irresponsible to wield analogies recklessly.

@Warsaw Will -
With their continuation, your apologies are beginning to seem less sincere. I am not bothered by someone who is genuinely having a hard time understanding something presented, regardless of on which side the problem lies. I am a bit bothered when someone makes an effort to place new obstacles in the path in what appears to be an attempt to prove that they were 'right all along' and that the idea is beyond all reasonable comprehension.
I will suspend my disbelief of your sincerity a bit longer and try to help you flesh this out on the increasingly more remote chance that you really genuinely want to understand and have simply failed to do so thus far. In exchange, I would appreciate it if you would extend me the courtesy off letting me know that you are not engaged in anything remotely like teaching creative writing.
To begin with, grocery stores, around here at least, do not require any positive identification of sex nor a declaration of gender to enter the store. Similarly, the police do not make regular stops to confirm that everything in the car has a specific gender or sex. To top it all off, the English language, unlike a number of other languages, does not even assign a specific sex to the majority of words.
With no disrespect to Brus here, you have to be reading a lot into a comment that isn't there, or have pretty low standards to consider 'What' worthy of distinction as 'pithy'.
The world is filled with possibilities, not impossibilities. Warsaw Will, do you ever talk things out in your head?....have a conversation with....yourself? I'm here to let you know that you don't have to leave 'yourself' in a kennel at home when you go to the grocery store. Yourself can accompany you and you and yourself can continue talking it our in your head, in the grocery store.
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Perhaps if you stop leaving it caged every time you leave the house, you will be able to work out this relatively simple hypothetical soon.
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Sure, Brus, it might be an imaginary friend. Just to reiterate, there is no requirement that imaginary friends be assigned a specific gender or have a specific sex.

Walrus Will,
Would you allow 'It and I are going to the store'?
What if I later confided in you that 'it' was just a character that I made up to keep me company, and told you that ''It' was actually me/I'.
Let's further pretend that this confused you and you asked, 'Well if you are it, then who was the 'I' you were referring to when you spoke of going to the store together?'
To which I would feel the need to respond by explaining, 'It and I are both _____'.
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Still too turbid? Hopefully you understand the possibility for this to arise. It is actually still English, even if it is a part that makes you less than comfortable,

Thanks for the response Warsaw Will...
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"...."I just have to be ____" - 'me' or 'I'? I would suggest neither, but - 'myself'...."
-I like this answer even if it doesn't technically answer the question. When someone inquires whether 'It is I' or 'It is he/she' is correct, would you say 'no' and instead suggest 'It is myself'?

"...."I am _____"- 'me' or I''? again neither - 'I am what/who I am'...."
-Once again I find myself liking your answer, and also curious how it relates to other constructs. If someone were to inquire on the phone if they were speaking to ______ your formal name), do you think it is advisable to respond with "It is what/who I am"?
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"....I'm afraid I don't understand your last two sentences. How can 'it' and 'I' be 'me' or 'I'. Sorry, but I can't make out the sense of these sentences..."
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Hopefully I can help clear up any confusion.
Since 'it' can be a variety of things, simply replace it with something that plausibly might not have been realized to actually be ones own person....
"We have seen the enemy and it is us"
"It turns out, all along it wasn't some other person holding me back. It and I have always been, currently are, and always will be _____" -'I' or 'me'
'this is not a matter of explicit naming; 'the same person' is not in the set of choices.

I am of the opinion that 'It is I' is correct.
It does however make me wonder about constructs like;
"I just have to be ____" - 'me' or 'I'?
"I am _____"- 'me' or I''?
"With that insight, I realized that in this context, it and I are both _____" - 'me' or 'I'?
"It and I have always been, currently are, and will always be ______" - 'me' or 'I'?

I am of the opinion that 'It is I' is correct.
It does however make me wonder about constructs like;
"I just have to be ____" - 'me' or 'I'?
"I am _____"- 'me' or I''?
"With that insight, I realized that in this context, it and I are both _____" - 'me' or 'I'?
"It and I have always been, currently are, and will always be ______" - 'me' or 'I'?

I am of the opinion that 'It is I' is correct.
It does however make me wonder about constructs like;
"I just have to be ____" - 'me' or 'I'?
"I am _____"- 'me' or I''?
"With that insight, I realized that in this context, it and I are both _____" - 'me' or 'I'?
"It and I have always been, currently are, and will always be ______" - 'me' or 'I'?

Hairy Scot,
The example you suggest is not only awkward, but grammatically incorrect:
"....The government has been advocating that the community to recycle more.....".
Read it out loud to yourself...every word. No one speaks like that. Well, I guess you just did. I'll rephrase, any who speaks like that is likely to have a hard time retaining the respect of others.
If you are going to advocate for a specific use, you should probably at least read it out loud to make sure it sounds correct, before publishing.
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'...for the community to recycle more.'
or
'...that the community recycle more.'