@Ted Clayton[S]omething I’ve seen on numerous other sites is the ability to up or downvote a comment.

This feature stokes visitation & participation. You can see that some regulars are dropping by quickly, just so they can get in/freshen their Votes.

There are often kinda-gross downsides, but these problems look like they should be remediable.

I think it's bad & wrong, to use voting to pressure certain commentors to STFU. To make people 'disappear', because others simply disagree with them.

Vote-widgets can get downright ugly, to be perfectly honest with ya. But it does not have to be that way; the Admin has settings that can either let voters turn into thugs ... or enable the Edward Snowdens to sound-off with impunity.

'Traditionally', voting has been used to flatter members of the insider-clique, who use it to kick sand in the face of noobs and trap-door those who's politics are at the opposite pole. Bummer.

I recommend voting, and several other things like it. It's not a meaningful enhancement for the website, but it is a lot of fun for participants . I think these things are fairly easy & unproblematic technology - which counts. Just beware that it's an ill-mannered steed, and needs a firm hand.