Hi,
Thanks
When you edit a custom field in the HikaShop backend (Display > Custom field), you will see some HikaMarket specific options in the right column, for the "display".
Thanks to that options you can configure if you want the custom field be editable (or display) for the vendors.
For the product description issue ; I think the best will be to use a custom plugin so you can filter the description text in order to remove some content.
I don't know how you want to filter the content exactly so it will be difficult to say more, but it can be a brutal "strip tags" (to remove all HTML content) or a more complicated replacement by regular expressions
Regards,.
Jerome - Obsidev.com
HikaMarket & HikaSerial developer / HikaShop core dev team.
Also helping the HikaShop support team when having some time or couldn't sleep.
By the way, do not send me private message, use the "contact us" form instead.