Incorporate charleskorn's feedback

docs/sources/mimir/release-notes/v2.15.md

@@ -39,7 +39,7 @@ HTTP client settings can now be tuned for GCS and Azure backends via an `http` b
 
 The compactor now refreshes deletion marks concurrently when updating the bucket index.
 
-The number of Memcached replicas for each type of cache can now be set using  configuration settings when using jsonnet.
+The number of Memcached replicas for each type of cache can now be set using configuration settings when using jsonnet.
 
 ## Important changes
 
@@ -77,11 +77,11 @@ The following deprecated configuration options were removed in this release:
 Grafana Mimir 2.15 includes some features that are experimental and disabled by default.
 Use these features with caution and report any issues that you encounter:
 
-A streaming PromQL engine can now be enabled with `-querier.query-engine=mimir`.
+Mimir's experimental PromQL engine can now be enabled with `-querier.query-engine=mimir`. This new engine provides imrpoved performance and reduced querier resource consumption; however, it supports only a subset of all PromQL features. IT will fall back to Prometheus' engine for queries containing unsupported features.
 
 The query-frontend can now cache non-transient errors using the experimental flags `-query-frontend.cache-errors` and `-query-frontend.results-cache-ttl-for-errors`.
 
-The query-frontend and querier both support an experimental PromQL function, `double_exponential_smoothing`, which can be enabled by setting `-querier.promql-experimental-functions-enabled=true` or `-query-frontend.promql-experimental-functions-enabled=true`.
+The query-frontend and querier both support an experimental PromQL function, `double_exponential_smoothing`, which can be enabled by setting `-querier.promql-experimental-functions-enabled=true` and `-query-frontend.promql-experimental-functions-enabled=true`.
 
 The ingester can now support out-of-order native histogram ingestion via the flag `-ingester.ooo-native-histograms-ingestion-enabled`.
 
@@ -118,7 +118,6 @@ The distributor now supports promotion of OTel resource attributes to labels via
 - Querier: Fix stddev+stdvar aggregations to always ignore native histograms, and to treat Infinity consistently.
 - Query-frontend: Fix issue where sharded queries could return annotations with incorrect or confusing position information.
 - Query-frontend: Fix issue where downstream consumers may not generate correct cache keys for experimental error caching.
-- Query-frontend: Fix `QueryFrontendCodec` module initialization to set lookback delta from `-querier.lookback-delta`.
 - Query-frontend: Support `X-Read-Consistency-Offsets` on labels queries too.
 - Ruler: Fix issue when using the experimental `-ruler.max-independent-rule-evaluation-concurrency` feature, where the ruler could panic as it updates a running ruleset or shutdowns.