FYI, it majorly ticks people off if you use the Hal Jordan/ Green Lantern tags when the post is actually about Batman/ Superbat/ the Batfam and Hal/ another Lantern is simply a side character/ plot device.
It's a numbers thing: the Batman tag has 1.8 Million followers vs Green Lantern with less than 6500. By tagging Hal literally every time he's mentioned, people are making it hard to actually find content about Hal in his own tag.
And no, you can't just block people either, because it's always a different person! It's not an issue with any single person. No one would bat an eye about 1 in 100 or even 1 in 50 batposts. But they make up a very significant chunk of the tagged content.
It's forcing people to play the world's most annoying game of whack-a-mole. (And I don't even want to play it, because I actually like Batman, especially your stuff. Just.. not when I'm searching for Hal content lmao.)
I obviously can't force you and other people to change the way you tag. But I can beg you to consider it. So here I am.
Okay, I'm going to say this as gently as possible because I keep getting asks like these and I don't really think we're on the same page. There are a few points I want to get out of the way before I talk about tagging itself.
You are frustrated because there is a lack of Hal Jordan content
You are frustrated because there is a lack of high quality Hal Jordan content
You are frustrated because Hal Jordan content is not as popular as Batman content
Tag "etiquette" is a rapidly evolving and nebulous thing, and I don't think it's as straightforward as you and other tag purists make it out to be. There are some core components more people agree on - tagging hate in a different tag, for example - but beyond that?
You cannot control what other people tag, like you suggest. And I want to suggest to you, that asking people to not tag a character when they are making a post about them/involving them is a well-intentioned but impossible request.
Here's why: You mention that you don't enjoy finding posts where Hal Jordan is a "side character" or "plot device." The problem is, if Hal Jordan is mentioned by name in the post, that's a pretty straightforward tag for the average Tumblr user. "Oh, Hal has a line in this mini chat fic? I'll tag him." They're not thinking about catering to your experience, or your desire to see exclusive, high-quality Hal Jordan content. They're tagging the guy because he shows up in the post, full stop.
Another issue is the ability to filter in the opposite direction -- without tagging Hal Jordan in posts, you also remove the ability for other users to filter him out of posts, regardless of his role "size" in that post. If he's not tagged, he's harder to filter around. That's why we have tags - to find and to avoid content.
I got feedback while writing love comes quickly that I shouldn't have tagged Batlantern in my posts about their jealousy/love triangle because the Batlantern wasn't "endgame." The problem was, Batlantern literally happened in that fic. It happened in the posts. And so I tagged those posts with the ship, because guess what? The posts were about Batlantern. They weren't "endgame", but that's not how tagging works. It's how you want it to work, but that's not how most people think or have used tags.
I think the overall problem here is that you, and other fans (I've seen this same discourse about Duke and other characters who don't get enough "fandom time") use the Tumblr tag as a way to find and enjoy content about your favorite character. There's nothing wrong with that, but it involves a ton of sifting. And yes - even those in the Batfamily/Batman tags have to do this, too.
Where we differ in opinion, I suspect, is that I don't think sifting through your character tag is a great way to find high quality, character-focused posts. And I don't think we should expect it to be. The tag is an unedited, unfiltered swill of a variety of posts -- some with Hal Jordan as the focus, some with him as a secondary JL character, and some where he's mentioned in passing.
I see people get very defensive and "protective" of these character tags, and you correctly identify that that kind of protectiveness is fruitless. I posit that it is because you, not the random accounts tagging Hal Jordan on a JL post, are using the tag filter/search incorrectly. You have expectations for Tumblr that are neither realistic for the platform, nor how it has been historically used.
But listen -- the tag search is the place you start. You sift, you filter out posts, and eventually you find blogs that post high-quality content that focuses on your character exclusively. You follow those blogs, and eventually your dashboard is the stream of Hal Jordan-focused posts, both new and reblogged, that you want the character tag to be.
The problem is, as I suspect you've seen, there just aren't as many Hal Jordan or Duke-focused blogs putting out content at the rate of the Batman/Batfamily tags. And that's really disappointing, and I don't want to skip over that. It really sucks, and unfortunately sometimes our only option is to either 1) accept that 2) create our own content or 3) convince others to create content. But shaming people for using the tag "wrong" -- not what you're doing here, to clarify, but just what I've seen -- isn't the way to achieve #3 there at all. You just turn people off ever mentioning that character again.
You might think this is a harsh take, and you might think that I contribute to the issue you are experiencing. There is a way for people to use Tumblr and for you to enjoy your content. But it involves work on your end, and managing expectations. And of course, a general level of respect from people creating posts and tagging them. I hope you're not upset with this response, but I think it's the last I'll say on the subject.