Whether a known bug, as some sources claim, or a missing capability, SharePoint 2010 doesn't allow anything more than plain text to be used in a column on a library or picture library. Regardless, there is a workaround. An IT tech on our SharePoint team found the article "Add Multiline Rich Text/Enhanced Rich Text column to document library or picture library". Taking the steps described in the article, I was able to create a library with fully functioning multiline enhanced rich text columns. I'm reproducing the article here because the blog hasn't had a new post since July 22, 2010 and I'm concerned it won't persist.
- Go to Site Settings>Galleries>Site columns.
- Create a new site column (or columns) with the information type set as "Multiple
lines of text" and set the column to allow rich or enhanced rich text.
- Go to Site Settings>Galleries>Site content types.
- Create a new custom content type using a document content type as parent.
- Edit your new content type and add your new site column.
- Go to All Site Content and create a new document library. (This
library will not have the desired functionality)
- Go to your new library's Settings>General Settings>Advanced Settings and set "Allow management of content types?" to yes.
- When you return to your list's settings, the Content Types section will be visible. Select "Add from existing site content types"
- Select your new content type from the left list, click "Add >", then click OK. (Optional: When you return to the settings, you can remove the Document content type from your library if you don't want it to be on descendant libraries by default.
- Now, from your new library's Settings, in the Permissions and Management section, select "Save the library as template".
- Return to to All Site Content and create a new library using your new template.
The library created from your new template will have your new content type and its new custom rich text column(s). The fields will be fully functional in this library.
In keeping with SharePoint's arguably unintuitive, illogical, and incomplete functionality, rich text columns not added to the new content type and then the new template will not be fully functional even if the library was created from the new template, nor will adding another rich text field to the content type update the new template or any descendant libraries.