I did more research and I'll update my post, but Q posted one time with an ID that began with 0A9 in post number 234. I misspoke when I said tripcode.

for reference:

https://anontools.xyz/?text=0a9

ID: 0a9612 and it is also colored green to stand out.

I'll try and explain it the best I can, but I don't use 4chan so I'm probably not the best person to explain.

4chan is anonymous and the website assigns you an ID of random numbers and letters, how long this ID lasts I don't know, I'm guessing new ID per thread and also different if you are original poster. So different threads = different ID.

No one has an account or permanent handle, but anyone could use the handle Q. So to prove that Q is the same Q and not a bad guy pretending to be Q, Q had to constantly post with a tripcode which is a unique cryptograph of the password. As long as Q is still using the same password, the tripcode will be identical. Such as !UW.yye1fxo

Q would have to give a proof when he changed passwords, because each password will produce a new tripcode. A Q proof confirms the new tripcode that Q is using, and this happens each time Q needs to change password.

also, read:

https://www.reddit.com/r/NoStupidQuestions/comments/2u8ft8/how_exactly_does_4chan_work/