As someone who dabbles in philosophy of language, the part that kills me about the emojis are heiroglyphs discussion is that heiroglyphs are language and emojis aren't. Because heiroglyphs were/are used for language and emojis aren't. People seem to be coming in with the assumption that heiroglyphs have meaning because they're images that depict things. And, not to impute things to people, but it pairs really well with the assumption that heiroglyphs are somehow "inferior" or unsophisticated compared to the alphabetic orthographic system we have now.
But that's not how any of this works. Heiroglyphs have meaning because people used them for language, the fact that they sometimes are images is accidental. Imagine, for instance, a picture of bread with vertically-facing wavy lines above it. That could mean anything. It could mean "hot bread" or "rotten bread" or maybe it has nothing to do with bread. Maybe I've established with friends that when I text that picture of bread to them, I'm saying that eating fresh bread. Maybe I've established with other friends that when I text that picture of bread to them, I'm saying that I have a stomach bug. Then the meaning of that picture of bread is "I have a stomach bug". Signs have no meaning apart from their use. A picture of bread doesn't mean anything unless it's being used to mean something.
Heiroglyphs have meaning in the same exact way that modern alphabetic orthographic written scripts do - people used them to mean things in the same way we use written words to mean things now. Emojis aren't used by people to communicate certain propositions, ergo they're not language, ergo they're not heiroglyphs. There's no organized system of meaning people follow to impute meaning to strings of emojis. Because people aren't using them that way. As soon as people start using emojis as language, then they'll be heiroglyphs. As soon as people start using strings of solely emojis to communicate propositions, then they'll be heiroglyphs. But not until then. No string of emojis, no matter how long, will have meaning - until people are using them to communicate.
"👁️⌛🌡️🛀🏼🌛" could mean fucking anything, much in the same way the string of words "I ate lunch last week" could mean fucking anything. The reason the latter has meaning is because it's embedded within a system of human activity wherein it communicates the proposition [I ate lunch last week], but given a different system of human activity it could just as well communicate the proposition [the weather's nice today]. Until emojis are incorporated into a system of human activity to communicate propositions, no string of emojis will mean anything ever.
Let's make it very simple! (and I do mean simple, we're not going for 'well technically' here)
Hieroglyphs are a script and that script is used to write three different stages of the Egyptian language: Old, Middle, and Late Egyptian.
Hieroglyphs are referred to as 'logoconsonantal' which are 'logograms with consonant sounds attached to them' or 'pictures that reference spoken sounds'.
This is very similar to how we understand the Latin alphabet in so much as the letters have sounds attached to them and putting those letters with sounds together forms words.
The Egyptians formed words in their language using the Hieroglyphic script by putting together signs with the sounds needed to form the word. The word 'cat' in Egyptian is 'mjw' (pronounced onomatopoeically as mew) and is formed of 4 signs: 𓅓𓇋𓅱𓃠
The owl sign sounds as 'm', the reed leaf sounds as 'j', the quail chick sounds as 'w', and the cat is there as a determinative or 'marker' to make sure you're not reading it as any other word that is spelled 'mjw' (like 'metal instrument' (has an instrument determinative) or 'grief' (has a wailing woman determinative)).
Just as A, B, and C have set sounds, Hieroglyphs have set sounds, and that's how they spell words. It's really that simple. It's exactly how we do it, just with pictures representing sounds rather than letters.
Emojis cannot do any of this.
