IP-bans aren't very effective nowadays.

Use a random friend's IP or one of billion proxy servers
Look for example here: http://www.stayinvisible.com

If it seems too complicated way for you,
you can at least check the "Message format" check-box just above the "Subject" field before you post plain text logs.
With a single mouse click you can protect your plain text logs from corruption because of square brackets in the logs and the BBCode-parser.
And you also can keep the original format of the logs ( spaces, etc. ) this way.