Depends on your goal but i would suggest to use steemit comment picker for a random winner and then if the comment chosen makes sense with the contest then fine congrats if not then again steemit comment picker for a new potential winner !!
Make it fun ?? let the contest be crazy
Can we do this on a regular basis? Hell YES !!
So track with comments rather than a tag or something?
well using tags could also be something that is included in the contest..it would help filter comments.