Russ,
9. What about vibrato?

You won't hear it much. Most reels are full of 16th notes played at 120 bpm, with no time for vibrato. You might use it in waltz, but all ornaments in any style are subordinate to the rhythm. If there isn't room for the ornament "in the groove" we lose the ornament rather than lose the beat.end of quote
it is accepted by most traditional musicians as suitable in airs,although most musicians use a not so wide vibrato.
whoever wrote the above,is clearly not too well acquainted with trad music,in that they have forgotten to mention airs,airs are not the same as waltzes.