Looking ahead: expect confusion to arise from Apple's commonplace use of one word FileVault — without a version number — for two very different technologies.
(Versions 1 and 2 both involve encryption, but encryption is applied at totally different levels.)
Options (not mutually exclusive)
continue with one tag filevault for two different technologies
I can add the tag core-storage to questions that relate to FileVault 2. Example result:
If only a limited number of tags can be added to a question, this is not ideal.
I can do a little CHAOS-like housekeeping. Currently only six results to the following:
At the moment I can't recall the third option that came to mind, but I'll leave this question as a placeholder, to be revisited and edited very soon. Hopefully within the next twenty-four hours.
tag synonym legacy-filevault
Meta users: if you imagine any other options, please edit this question. Thanks :-)
We can not assume version 2 where FileVault is mentioned by a user of Lion. Both versions 1 and 2 can be used simultaneously.