I found the answer I was looking for in this forum thread:
But I don't think it is satisfactory. I am the web administrator of an organisation where several people are blogging. Some of these people have no HTML knowledge at all. I think it was great that you added the caption functionality for images. This was a real help, but then I also think you need to allow people to link from the caption, as well as italicise some of it.
We have people blogging about art and blogging about biology. Names of artworks have to be italicised, and latin names of species too. We would also like to link these to our website. So it would really be awesome if this part of the caption could be "freed".
Is it part of your plans for the future?
Thanks a lot,
The blog I need help with is blog.tepapa.govt.nz.