Editor/TinyMCE kills ? and many other HTML entities

hi,

adding entities in the code/html view of the editor like ? (⅔) only survive until the first save after switched to vistual mode in the editor. for me that mean the visual mode decodes the entities, shows them correctly, but then saves them wrong. after save only questionmarks remain on the place.

it is possible to hack this? maybe a plugin exists that i couldn’t find for this.. and when someone knows a plugin to replace custom defined charachters or strings automaticaly that would be greate. i would like to enter 2/3 and get ⅔ after save. now i have to enter ⅔ and it is not very handy and it get lost in the end. maybe this bug is an idea for bigger improvents.