Thank you for that and that's precisely right - it's "Read Only", not "barred". Non-paying guests will still be able to read almost everything on the boards, except WSCC Members Only, and Sponsors & Traders areas. They just won't be able to start new threads or post replies, use the Search facility or use the PM system, for free.
The whole point of Trial Club Membership is to allow people to have 30 free days to wander around the boardroom, and 20 free posts in that time, to question others and make up their own minds as to if whether or not what club membership offers for them personally is a sufficient value proposition for their needs. If they still can't decide, they can buy another 60 days for a tenner and have full unlimited membership posting rights. That's good for everyone.
(For the record, there are fewer than 10 accounts that are "banned" out of 9,413 total registered.)