I had a more elaborate post written up as to address the - somewhat valid, honestly - points you made, but my clumsy fingers deleted all of it (and then reloaded, so I can't even CTRL+Z, rip). Sorry for the delay.
There seem to be two primary concerns you have:
That (primarily new) players who frequent the forums are unable to understand what threads in Alliance Affairs are about,
That tags will be used in other sections of the forum.
While I agree with the idea that the integration of new players in the overall Orbis community is a good thing, I fundamentally disagree with the idea that, most, or even a significant amount of, threads are confusing. If a player were to read the first post, and then the few posts that come after, you would find no shortage of explanations with regards to the content of the thread. Moreover, some threads are intentionally confusing, and forcing players to add tags in their thread title - which, I suppose, is your prerogative, as is my duty to argue for what I believe in - simply make the point of those threads (to confuse and bedazzle) irrelevant. In my opinion, threads that are confusing to new players will largely seem so because they lack in-game knowledge and/or context, not that they aren't clear in their message.
Let us look at the past, hm, 15 threads in this subforum.
This thread is announcing the cancellation of a treaty. It says so in its first three lines.
This thread is announcing the existence of a new alliance (it gives a tl;dr too) and the posts that follow make that point abundantly clear.
This thread has some flavour content in the beginning, and explains what it's about in the last line of the post.
This thread is Inst being weird Hyperion announcing their 'bonds' program and giving a somewhat lengthy explanation of what that implies.
This thread, while somewhat hard to understand due to - presumably - the OP's level of mastery of the language, announces fairly clearly that they are recognizing a state of hostilities with BK and are confused as to why this happened.
This thread is a DoW and contains the target's name in the first paragraph.
This thread wouldn't fit your rules anyway, but I am including this to highlight my point about cultural references and why confusion will persist unless players actively attempt to integrate themselves within the community. It's a log dump that is fairly straightforward, however.
This thread explains its contents in the title, anyway.
This thread very clearly explains its purpose.
This thread, yeeaahhh, we weren't too sure what was going on here either (It's a collection of inside jokes and memes that have gone for too long to explain just by the use of a tag, and is meant to be confusing)
This thread says what it's about in the title. It's also meant to be 'confusing' (if anyone checks the alliance affiliation it would be clear as to what happened).
This thread, while yet another part in a very long sequence of inside jokes/memes, lays its jokes out pretty clearly. This is the sort of funny thing that would be marred, not going to go so far as to say it would be ruined, by the usage of title tags.
This thread was just click-bait. It didn't serve any purpose, as was explained a few posts down.
This thread is hilarious and adds cultural flavour because it's "confusing" (it says exactly what it's about, people just need to read). Also, if you scroll down below you'll see further explanation.
This thread is Sketchy posting Polaris' failure in guarding their bank. It provides an altered flag, a screenshot of the bank loot, and text to... explain it.
My point is, the vast majority of the threads that people are 'confused by' are either spam, meant to be confusing (when in reality it takes only a bit of inferring to understand what they're about), or abundantly clear, they just don't say it in their thread title. If new players are confused with what is being said, they should, well, read the posts that come after the OP. More often than not it explains the thread's purpose quite clearly.
As for the second concern I laid out in the beginning of this (now somewhat lengthy) post, there are three possible outcomes to tags being used out of this subforum:
They spam tags, in which case a one minute edit by mods is all that is needed to remove those tags,
They add one or two tags, which... isn't actually a problem. Why would it be?
They don't use the tags, which is fine.
Anyway, my point with this all is that it seems like artificial spoon feeding that won't accomplish anything but actually remove the one incentive players have to integrate themselves in communities (to understand what the frick is going on in Orbis).