Users are able to access their personal space (if created) by going to the following URL:

<domainURL>/display/~username

If the user is removed from the Confluence Internal Directory, the personal space also gets deleted. However, if the user is from an external source (e.g. Crowd, JIRA, or LDAP) and is removed from that source, accessing to the user's personal space with domainURL>/display/~username will yield a "Page Not Found"

However, the personal space is still accessible when there is a valid page title defined in the URL:

<domainURL>/display/~username/A+Valid+Page+Title

Additionally, the content remains searchable.

It seems it would make more sense if the personal space of the user is no longer accessible if a user is removed from any source, internal or external.