I'm running the Sublime Text 3 Beta Build 3047 on Linux with Vintage Mode enabled.
The ";" and "," motion keys are supposed to navigate to the next occurence of the character given in the last "f" motion.
In the following example file:
This is an interesting example line.
Starting with the cursor at the beginning of the line, 'f i' will correctly navigate to the 'i' in 'This'. Successive 'f i' commands will move to the different 'i's in the line. However, ';' and ',' do not move the cursor at all.
This problem never occured for me in Sublime Text 2.