Well, there's a slight snag here, due to be solved real soon now. As I understand it, the mailing list program used by libreoffice in its present version can not accept unmoderated posts sent via gmane unless the sender is also registered with libreoffice. Also as I understand it, this is due to change in an upcoming version of the mailing list program.
This means you have two choices at present.
1. You can register with the libo mailing list using the -nomail parameter. This means that your posts via gmane get right through the system, but you don't get any emails. You read the newsgroup in your nntp reader. To use this option send an email from the same email account you registered with gmane to <listname>+subscribe-nomail@global.libreoffice.org. Reply to the resulting email and you're done. Listname for the users list is, of course, users.
2. You don't register with the libo mailing list, which means that, until the list manager is updated, your posts will come to one of the moderators to be approved before getting on the list. Normally this seems to result in a delay to be reckoned in minutes rather than hours.
HTH
//James
One of the moderators