docs: Update service/node identities text on ACL index (#13022)

Modify node and service identities paragraphs on ACL index to better
conform with the style guide.

Co-authored-by: Jeff Boruszak <104028618+boruszak@users.noreply.github.com>

website/content/docs/security/acl/index.mdx

@@ -69,7 +69,7 @@ Refer to the [Roles](/docs/security/acl/acl-roles) topic for additional informat
 
 ## Service Identities
 
-Service identities are configuration blocks that you can add to role configurations or specify when linking tokens to policies. They are used during the authorization process to automatically generate a policy for the service(s) specified. The policy will be linked to the role or token so that the service(s) can _be discovered_ and _discover other healthy service instances_ in a service mesh.
+Service identities are configuration blocks that you can add to role configurations or specify when linking tokens to policies. You can use them during the authorization process to automatically generate a policy for specific services. The policy is linked to the role or token, allowing the services to be discovered and to discover other healthy service instances in a service mesh.
 
 Service identities enable you to quickly construct policies for services, rather than creating identical polices for each service.
 
@@ -80,9 +80,9 @@ Refer to the following topics for additional information about service identitie
 
 ## Node Identities
 
-Node identities are configuration blocks that you can add to role configurations or specify when linking tokens to policies. They are used during the authorization process to automatically generate a policy for the node(s) specified. You can specify the token linked to the policy in the [`acl_tokens_agent`](/docs/agent/options#acl_tokens_agent) field when configuring the agent.
+Node identities are configuration blocks that you can add to role configurations or specify when linking tokens to policies. You can use them during the authorization process to automatically generate a policy for specific nodes. When you configure the agent, you can specify the token linked to the policy with [`acl_tokens_agent`](/docs/agent/options#acl_tokens_agent).
 
-Node identities enable you to quickly construct policies for nodes, rather than creating identical polices for each node.
+Use node identities to quickly construct policies for multiple nodes, rather than creating identical polices for each individual node.
 
 Refer to the following topics for additional information about node identities: