The meaning will change ever so slightly, that if you didn't look for it, you wouldn't know.
The original sentence means "The delimiter does not have to be a bracket and it is possible to imagine that the delimiter can be any character."
Extract the "conceivably any character" and change it to "any conceivable character", and you changed the object "conceivably/conceivable" is modifying. In the second sentence, the meaning would have been changed to be:
The delimiter does not need to be a bracket, but can be any character that you could possibly think up of.
Thus, the change in meaning is very slight, but the original intent of the author would be changed if you were to changed those words ever so slightly.