Apply suggestions from code review

Co-Authored-By: Mazdak Farrokhzad <twingoow@gmail.com>

Author: RalfJung

src/behavior-considered-undefined.md

@@ -1,13 +1,13 @@
 ## Behavior considered undefined
 
 Rust code is incorrect if it exhibits any of the behaviors in the following
-list. This includes code within `unsafe` blocks and `unsafe` functions!
+list. This includes code within `unsafe` blocks and `unsafe` functions.
 `unsafe` is not an excuse to cause undefined behavior.
 
-It is the programmer's responsibility when writing `unsafe` code that it is not
+It is the programmer's responsibility when writing `unsafe` code to ensure that it is not
 possible to let `safe` code exhibit these behaviors. `unsafe` code that
-satisfies this property for any `safe` client is called *sound*; if `unsafe`
-code can be misused by `safe` code to exhibit undefined behavior, it is
+satisfies this property for any safe client is called *sound*; if `unsafe`
+code can be misused by safe code to exhibit undefined behavior, it is
 *unsound*.
 
 <div class="warning">