I think this particular scheme is practically reversible, with occasional ambiguities, but only if the second stage is reversible (the digit is unambiguously identified by the glyph). Maybe with some practice it's possible to learn to read it slowly without external tools.
For example (suppose we know that the plaintext is in English and the spacing is preserved):
4631524 3933 46315 3856852 768 3925 96 62 566
Let's start with the short words: 96 and 62.
96 is (I | US | Z) + (F | O | T), given English it's either IT or IF.
62 is (F | O | T) + (B | K | R), there should be a vowel, so it starts with O and the word is OR. (Edit: or could be OK, which would work for IF OK, so it's more ambiguous than I thought, but I still think it's possible to deduce the correct plaintext.)
Now, IF OR looks odd, so it's more likely IT OR.
Then 566 and 768.
566 is (E | N | X) + (F | O | T) + (F | O | T), even without the context given by IT OR ..., I see only one word here: NOT (which means all standalone 566's in the text will be not's)
768 is (G | P | Y) + (F | O | T) + (H | Q | U), this one is very easy, given the first and the last letters are relatively rare. I can only see YOU here and no other alternatives.
So, we have:
YOU 3925 IT OR NOT. It's possible to just guess and check, but let's try and do it the slow way:
3925 is (C | L | W) + (I | US | Z) + (B | K | R) + (E | N | X), let's try 9 as I as the most frequent, especially given the first letter is a consonant (also there is a possibility of CUS/LUS too): YOU ?I?? IT OR NOT. The ending is I + (B | K | R) + (E | N | X), which given normal letter combinations in English is most likely I + (B | K | R) + E, so YOU ?I?E IT OR NOT. Not that many words would work here (C | L | W) + I + (B | K | R) + E, like WIRE, but this is most likely LIKE.
4631524 3933 46315 3856852 YOU LIKE IT OR NOT
Now we can just check if WHETHER fits 3856852 and then there are only 3 words left to crack.
3933 is (C | L | W) + (I | US | Z) + (C | L | W) + (C | L | W), etc.
I think after a while one will get used to common combinations of symbols and the decoding will get much easier.
For example (suppose we know that the plaintext is in English and the spacing is preserved):
4631524 3933 46315 3856852 768 3925 96 62 566
Let's start with the short words: 96 and 62.
96 is (I | US | Z) + (F | O | T), given English it's either IT or IF.
62 is (F | O | T) + (B | K | R), there should be a vowel, so it starts with O and the word is OR. (Edit: or could be OK, which would work for IF OK, so it's more ambiguous than I thought, but I still think it's possible to deduce the correct plaintext.)
Now, IF OR looks odd, so it's more likely IT OR.
Then 566 and 768.
566 is (E | N | X) + (F | O | T) + (F | O | T), even without the context given by IT OR ..., I see only one word here: NOT (which means all standalone 566's in the text will be not's)
768 is (G | P | Y) + (F | O | T) + (H | Q | U), this one is very easy, given the first and the last letters are relatively rare. I can only see YOU here and no other alternatives.
So, we have:
YOU 3925 IT OR NOT. It's possible to just guess and check, but let's try and do it the slow way:
3925 is (C | L | W) + (I | US | Z) + (B | K | R) + (E | N | X), let's try 9 as I as the most frequent, especially given the first letter is a consonant (also there is a possibility of CUS/LUS too): YOU ?I?? IT OR NOT. The ending is I + (B | K | R) + (E | N | X), which given normal letter combinations in English is most likely I + (B | K | R) + E, so YOU ?I?E IT OR NOT. Not that many words would work here (C | L | W) + I + (B | K | R) + E, like WIRE, but this is most likely LIKE.
4631524 3933 46315 3856852 YOU LIKE IT OR NOT
Now we can just check if WHETHER fits 3856852 and then there are only 3 words left to crack.
3933 is (C | L | W) + (I | US | Z) + (C | L | W) + (C | L | W), etc.
I think after a while one will get used to common combinations of symbols and the decoding will get much easier.