You probably don't want Sydent

Fixes #22.

README.rst

@@ -1,3 +1,18 @@
+What is Sydent?
+===============
+
+Sydent is an `identity server <https://spec.matrix.org/v1.6/identity-service-api/>`_ for the `Matrix communications protocol <matrix.org>`_. It allows Matrix users to prove that they own an email address or phone number, and allows _other_ Matrix users to look them up using that email address or phone number.
+
+Do I need to run Sydent to run my own homeserver?
+-------------------------------------------------
+
+Short answer: **no**.
+
+Medium answer: **probably not**. Most homeservers and clients use the Sydent instance run by `matrix.org`, or use no identity server whatsoever.
+
+Longer answer: if you want to allow user lookup via emails and phone numbers in a private federation of multiple homeservers, Sydent _might_ be useful for you. If you want to your homeserver to be able to verify phone numbers via SMS and you have an API token for the OpenMarket HTTP SMS API, then Sydent might be useful for you.
+
+
 Installation
 ============
 
@@ -127,7 +142,7 @@ Environment variables
 +--------------------+-----------------+-----------------------+
 | Variable Name      | Sydent default  | Dockerfile default    |
 +====================+=================+=======================+
-| SYDENT_SERVER_NAME | *empty*         | *empty*               |
+| SYDENT_SERVER_NAME | **empty*         | *empty*               |
 +--------------------+-----------------+-----------------------+
 | SYDENT_CONF        | ``sydent.conf`` | ``/data/sydent.conf`` |
 +--------------------+-----------------+-----------------------+