;doc: update command help

hledger/Hledger/Cli/Commands/Print.txt

@@ -109,19 +109,31 @@ options The output formats supported are txt, beancount, csv, tsv, json
 and sql.
 
 Experimental: The beancount format tries to produce Beancount-compatible
-output. It is very basic and may require additional manual fixups:
+output, as follows:
 
 -   Transaction and postings with unmarked status are converted to
-    cleared (`*``) status.
+    cleared (*) status.
--   Transactions' payee and or note are wrapped in double quotes.
+-   Transactions' payee and note are backslash-escaped and
+    double-quote-escaped and wrapped in double quotes.
 -   Transaction tags are copied to Beancount #tag format.
--   Account name parts are capitalised, and if the first account name
+-   Commodity symbols are converted to upper case, and a small number of
-    part is not one of Assets, Liabilities, Equity, Income, or Expenses,
+    currency symbols like $ are converted to the corresponding currency
-    "Equity:" is prepended.
+    names.
--   The $ commodity symbol is converted to USD.
+-   Account name parts are capitalised and unsupported characters are
+    replaced with -. If an account name part does not begin with a
+    letter, or if the first part is not Assets, Liabilities, Equity,
+    Income, or Expenses, an error is raised. (Use --alias options to
+    bring your accounts into compliance.)
 -   An open directive is generated for each account used, on the
     earliest transaction date.
 
+Some limitations:
+
+-   Balance assertions are removed.
+-   Balance assignments become missing amounts.
+-   Virtual and balanced virtual postings become regular postings.
+-   Directives are not converted.
+
 Here's an example of print's CSV output:
 
 $ hledger print -Ocsv