Updating the Intents section of 2.5 to be more clear on ramifications (#437)

Author: viktorklang

README.md

@@ -139,7 +139,7 @@ public interface Subscriber<T> {
 | <a name="2.4">4</a>       | `Subscriber.onComplete()` and `Subscriber.onError(Throwable t)` MUST consider the Subscription cancelled after having received the signal. |
 | [:bulb:](#2.4 "2.4 explained") | *The intent of this rule is to make sure that Subscribers respect a Publisher’s [terminal state](#term_terminal_state) signals. A Subscription is simply not valid anymore after an onComplete or onError signal has been received.* |
 | <a name="2.5">5</a>       | A `Subscriber` MUST call `Subscription.cancel()` on the given `Subscription` after an `onSubscribe` signal if it already has an active `Subscription`. |
-| [:bulb:](#2.5 "2.5 explained") | *The intent of this rule is to prevent that two, or more, separate Publishers from thinking that they can interact with the same Subscriber. Enforcing this rule means that resource leaks are prevented since extra Subscriptions will be cancelled.* |
+| [:bulb:](#2.5 "2.5 explained") | *The intent of this rule is to prevent that two, or more, separate Publishers from trying to interact with the same Subscriber. Enforcing this rule means that resource leaks are prevented since extra Subscriptions will be cancelled. Failure to conform to this rule may lead to violations of Publisher rule 1, amongst others. Such violations can lead to hard-to-diagnose bugs.* |
 | <a name="2.6">6</a>       | A `Subscriber` MUST call `Subscription.cancel()` if the `Subscription` is no longer needed. |
 | [:bulb:](#2.6 "2.6 explained") | *The intent of this rule is to establish that Subscribers cannot just throw Subscriptions away when they are no longer needed, they have to call `cancel` so that resources held by that Subscription can be safely, and timely, reclaimed. An example of this would be a Subscriber which is only interested in a specific element, which would then cancel its Subscription to signal its completion to the Publisher.* |
 | <a name="2.7">7</a>       | A `Subscriber` MUST ensure that all calls on its `Subscription` take place from the same thread or provide for respective [external synchronization](#term_ext_sync). |