Hello Maurice, I am not quite sure what you specifically mean by render issue in firefox from the information you provided. Have I missed something or could you possible include a screenshot?
If you mean the extra text (starting with Normal 0 false false false EN-US-X-NONE-X-NONE), that is, as far as I understand a side effect of using a Microsoft mail client with some configuration to post or reply to a post. This problem, as well as any render issues in firefox are not currently tracked by the ixda bug tracker so I am sure the moderators would like to investigate this if you report it.
Anyway, you should probably use the little feedback button on the right side for reporting issues to ensure the attention of ixda moderators and developers.