This has already been discussed and identified as an exim bug on exim-users. 
Filing in bugzilla for completeness.

according to spec.txt chapter 6.4[1], the following configuration
should be acceptable to exim:

begin acl

acl_whitelist_local_deny:
  accept
    hosts = ${if exists{CONFDIR/local_host_whitelist}\
                 {CONFDIR/local_host_whitelist}\
                 {}}

CHECK_RCPT_LOCAL_LOCALPARTS = ^[.] : ^.*[@%!/|`#&?]

acl_check_rcpt:
  accept
    hosts = :

  deny
    domains = +local_domains
    local_parts = CHECK_RCPT_LOCAL_LOCALPARTS
    message = restricted characters in address

begin routers

begin transports

begin retry

begin rewrite

begin authenticators

However, exim flags it as incorrect:
Exim configuration error in line 9 of exim4.conf:
  error in ACL: unknown ACL condition/modifier in "CHECK_RCPT_LOCAL_LOCALPARTS 
= ^[.] : ^.*[@%!/|#&?]"

Fixed in release 4.63.