Update spec/abci++/abci++_app_requirements_002_draft.md spec/abci++/abci++_basic_concepts_002_draft.md

Co-authored-by: William Banfield <4561443+williambanfield@users.noreply.github.com>

spec/abci++/abci++_app_requirements_002_draft.md

@@ -67,8 +67,8 @@ of `ProcessProposal`. As a general rule `ProcessProposal` _should_ always accept
 According to the Tendermint algorithm, a correct process can broadcast at most one precommit message in round $r$, height $h$.
 Since, as stated in the [Description](#description) section, `ResponseExtendVote` is only called when Tendermint
 is about to broadcast a non-`nil` precommit message, a correct process can only produce one vote extension in round $r$, height $h$.
-Let $e^r_p$ the vote extension that the Application of a correct process $p$ returns via `ResponseExtendVote` in round $r$, height $h$.
-Let $w^r_p$ the proposed block that $p$'s Tendermint passes to the Application via `RequestExtendVote` in round $r$, height $h$.
+Let $e^r_p$ be the vote extension that the Application of a correct process $p$ returns via `ResponseExtendVote` in round $r$, height $h$.
+Let $w^r_p$ be the proposed block that $p$'s Tendermint passes to the Application via `RequestExtendVote` in round $r$, height $h$.
 
 * Requirement 6 [`ExtendVote`, `VerifyVoteExtension`, coherence]: For any two correct processes $p$ and $q$, if $q$ receives $e^r_p$
   from $p$ in height $h$, $q$'s Application returns Accept in `ResponseVerifyVoteExtension`.

spec/abci++/abci++_basic_concepts_002_draft.md

@@ -215,7 +215,7 @@ The Application may also choose not to include any vote extension.
 When another process receives a precommit message with and vote extension, it calls
 method `VerifyVoteExtension` so that the application can validate the data received.
 If the validation fails, the precommit message will be deemed invalid and ignored
-by Tendermint. This has strong implications on Tendermint's liveness.
+by Tendermint. This has negative impact on Tendermint's liveness, i.e., if repeatedly vote extensions by correct validators cannot be verified by correct validators, Tendermint may not be able to finalize a block even if sufficiently many (+2/3) of the validators send precommit votes for that block. Thus, `VerifyVoteExtension` should only be used with special care.
 As a general rule, an Application that detects an invalid vote extension SHOULD
 accept it in `ResponseVerifyVoteExtension` and ignore it in its own logic.
 
@@ -261,7 +261,7 @@ Sources of non-determinism in applications may include:
     * Library version changes
     * Race conditions
     * Floating point numbers
-    * JSON serialization
+    * JSON or protobuf serialization
     * Iterating through hash-tables/maps/dictionaries
 * External Sources
     * Filesystem