I cannot reproduce the exact issue here (only if the linked text is one word longer than 27 characters, and not passed as the optional parameter).
If you are using the "DragonByte Tech: Advanced User Tagging" mod, this is known to cause the issue, since it requests that the wiki parser recurse itself. This is a bug in that mod. Re-calling the parser causes word-wrapping on already word-wrapped areas (or areas that word-wrapping skipped on purpose). It might also double-HTML-safe some things which wouldn't look right. Ideally, it should set the word-wrap character limit to 0 during its second parse, or more ideally, do its parsing during the first parse. If disabling the mod helps, I would suspect that this is also a bug in vBulletin that applies word wrapping to text that is part of an HTML tag.