Why RCS1098 is enabled by default?

Avoid 'null' on the left side of a binary expression

null==a in C# means ReferenceEquals(a,null)

https://stackoverflow.com/questions/34229318/should-null-be-checked-on-the-left-or-right-hand-side

https://stackoverflow.com/questions/970334/is-referenceequalsnull-obj-the-same-thing-as-null-obj

https://stackoverflow.com/questions/4850053/what-is-good-practice-for-null-reference-checks