Update feature_flags doc with clarification

doc/operations/feature_flags.md

@@ -105,6 +105,9 @@ For example, set a value of 15% to enable the feature for 15% of authenticated u
 
 The rollout percentage can be from 0% to 100%.
 
+NOTE: **Note:**
+Stickiness (consistent application behavior for the same user) is guaranteed for logged-in users, but not anonymous users.
+
 CAUTION: **Caution:**
 If this strategy is selected, then the Unleash client **must** be given a user
 ID for the feature to be enabled. See the [Ruby example](#ruby-application-example) below.
@@ -120,6 +123,9 @@ activation strategy.
 Enter user IDs as a comma-separated list of values. For example,
 `user@example.com, user2@example.com`, or `username1,username2,username3`, and so on.
 
+NOTE: **Note:**
+User IDs are identifiers for your application users. They do not need to be GitLab users.
+
 CAUTION: **Caution:**
 The Unleash client **must** be given a user ID for the feature to be enabled for
 target users. See the [Ruby example](#ruby-application-example) below.