The preview option for CHECKIN, CHECKOUT and HOLD_SLIP notices doesn't take account of whether the notice template is HTML or not and doesn't apply styling options.. as such it's not representative of the actual output.
Linking this to bug 33478, but in fact we're not taking any styling into account at all.. we should be taking the various style preferences into account as well as the localised styling per notice that's introduced in bug 33478