@flannan : appraisal blocking is not that good in the long run, a complete lack of skills should be very rare, and if it is ever discovered that there is someone who can not be appraised then a blank result becomes be on guard.
Now if it is common for beggars to have no skills then it could be useful, but would have limits for intelligence gathering since beggars are not exactly likely to be part of back room deals.
What you want is appraisal result forging, which might be easier with his result blocking.
@sjmcc13 All they have to do is not stand out and have inconsistency that detective minded individual could catch like this spell can be used only with this magic skill or this sword can only be wielded if the strength level is this amount. The reading does not match what actual capabilities show.
@Brize
That assumes that royalty must marry high nobles or other royalty. Thats not always the case. I've read novels where the king / queen needed to wed a commoner, and others where marrage partners were more based on individual power and capabilities. There have also been cases where the next ruler was chosen not from the last rulers family, but was chosen from a pool of higher nobles. So its more of what setting the author is going for.