If you export your bookmark from Diigo, make sure you use the Delicious export, not the Netscape export. (Their Netscape export is broken, and they don't seem to be interested in fixing it.)
To correctly import the tags from a [SemanticScuttle](http://semanticscuttle.sourceforge.net/) HTML export, edit the HTML file before importing and replace all occurences of `tags=` (lowercase) to `TAGS=` (uppercase).
You can use the third-party tool [Derefind](https://github.com/ShawnPConroy/Derefind) to convert refind.com bookmark exports to a format that can be imported into Shaarli.
Your bookmarks will be imported in Firefox, ready to use, with tags and descriptions retained. "Self" (notes) shaares will still point to the Shaarli instance you exported them from, but the note text can be viewed directly in the bookmark properties inside your browser. Depending on the number of bookmarks, the import can take some time.
You may be interested in these Firefox addons to manage links imported from Shaarli