It works best with PositionMap to use PositionMap captions and descriptions. For one thing, it is possible to have both captions and descriptions. And for another, they are searchable and portable with the images they accompany, as they are separate files whose names start with the images' filenames. Jalbum comments are all in a single file.
But JAlbum comments are useful for proofreading. You can make the typeface larger so it is easier to read. The file can be spellchecked and proofread all at once, and if the filenames contain numbers (as most digital camera-generated filenames do), spellcheckers generally will overlook them.
So, I use the utility in JCaPPM (under the file menu) to convert my PositionMap descriptions to JAlbum comments. Then I spellcheck and proofread in Microsoft Word, and copy them back to PositioMap comments. (I usually don't bother with captions -- they are short and easy to check by eye.)
You do need to make sure not to copy captions back to descriptions, or vice versa -- or you will lose one or the other. Just in case, make a copy of the comments file under a different name each time before you copy it back.
Another glitch -- bug -- I've found: when you close JCapPM or move to a different image from the one that is open, JCapPM will write the non-proofread version of the caption and/or description back to the corresponding file. So, it's best to have an image open which you already have read carefully and which does not need further proofreading, or which you have excluded from your album.