No this is a oxwall problem more noticeable in firefox
I don't know what it does or how it does it but if you have 2 tabs open it Facebook and oxwall after some time of chat on both sites both become slow input text
Delete Facebook tab and restart it does not help
Delete or wall tab and restart it then both site text inputs work fine
Then after a hour or so both slow down again to the point of have to wait 3 minutes for the words you already typed to appear
Delete oxwall tab and reopen it and back to all good
Maybe it fills some temp directory in firefox