Thanks for the feedback Yonik, Mark, and Shalin.
Not outright requiring a JIRA seems fine, though for me personally I'd end up filing them since it doesn't take much longer than sending an e-mail, gives a a central place for discussion (like this one!) that won't be lost in the depths of mail archives, and gives a a referenceable name. Seems the benefit outweighs the cost to me.
On modifying CHANGES.txt I'm sensitive to to the concerns of keeping the changes in CHANGES.txt significant while also giving credit to contributors. Perhaps it makes sense it cases like this to just include the contributors name in the commit message [i.e. "SOLR-6624: Spelling mistakes in the Java source (Hrishikesh)]" and not add it to the CHANGES.txt? Thoughts?