The Toolkit’s Toggle Memo Column setting allows you to turn on and off the memo column individually in each account by adding a checkbox in YNAB’s View menu.
By making this setting available to you on a case-by-case (or account-by-account) basis instead of making it a universal setting (hiding the memo column across all accounts), you can strategically hide this column in accounts where you don’t include memos. That said, I’m a very strong advocate of using the memo field.
Note: Originally this setting had a issue that led to very wonky results in Firefox if you had scheduled transactions with any text in the Memo field. That bug has now been squashed and everything looks great.