This is a great post. People need to discuss and contemplate tags a lot more.
I like seeing average comments per post. It's worth considering that some tribes just auto-comment whenever you tag and encourage their members to do the same (lovely SPAM). Also, if you don't use their platform to post, they don't reward you as much.
I'm worried about tag abuse. If it isn't relevant people shouldn't tag it just to get some reward or something popular. Those tribes like palnet are okay because that's their aim (I cringe when people go overboard though), but tagging things like Steem when it isn't about Steem come to mind (this post is about using steem so it's good).
The newest thing I despise is hashtag abuse, to give out
$#!t reward tokens. These explain around 50% or more comments on a lot of posts. Some even disguise themselves as low brow curation which is cute.
I have a new theory about tagging. Make the first 2 specifics (tags, tagging, trending-tags, tag-tutorial) and the other 3 more general categories (tutorial, steem, community). After 5 it doesn't matter so put the associative tags there(PHC, marlians, planet, whatever).
The reason for the 2 tags being specific is because you will probably own the trending page in that category for a long time on Steem and better yet maybe even Google or other search engine. Don't get to dumb and tag something no one will search for like fhnwuioahfoiahfoaw.
For example, I tagged jeonse, buyeo and baekje recently (I'm not sure if anyone on steem ever uses these). Also, if you do forward on Twitter, Reddit, Facebook or whatever, your chances trending there and climbing in the search ranks go higher and higher again (onboarding and cross-platform potential).