No, you cannot EASILY remove the teflon sleeve. The reason is that the tightening of the uppermost nut (what I would call the gland nut) compresses the teflon a little and, over time, it takes the shape of the internal machine threads it is being compressed against.
Item 4 in the pic is what you want to remove after first slightly loosening item 2. Item 4 is a 1/8" BSPP male to 1/8" BSPP female adaptor that screws into ANOTHER adaptor in the boiler.
Simply loosening item 2 (the gland nut) and lifting out the probe MAY tear up the teflon due to scale buildup on the probe shaft. Yes, it would be rare, but you don't want to be the unlucky one.