the OP is talking about additional sitelinks that appear under your ad when in the banner position, not about description lines #1 and #2. Our Google rep has categorically told us that using symbols in your sitelinks is not allowed, however they aren't out actively looking for them. If however a competitor were to complain about you using symbols in your sitelinks, you would then face disapproval of those links. (This is UK based advice).
I've done it before with bullet points to the point where it was deemed "excessive". Our rep told us they were rejected, yes, but it wouldn't negatively affect campaigns (ie: hurt Quality Score). If anything it probably boosted QS because of increased clickthrough rates.
The use of symbols is fine if not overused. If you have it in all of your links and you have it going on all over your site then you will definitely raise flags and Google will take your ads down rather quickly.