A bug has been reported in the tagging system, where tags from one topic were incorrectly applied to another topic. DeanMarkTaylor shared an example of this issue and codinghorror removed the incorrect tags.
The discussion led to a broader conversation about the use of tags in Discourse. codinghorror suggested that tags should be used sparingly and only for specific, relevant concepts. DeanMarkTaylor emphasized the need for tag merging and aliasing to prevent tagging issues.
Mittineague recommended limiting tag creation to administrators to prevent misuse. cpradio noted that Discourse allows setting a trust level for tag creation, which can help control the tagging process. Mohammad and codinghorror agreed that multiple tags are not necessary and can be counterproductive. Finally, sam suggested setting the minimum trust level for tagging to TL2.
I remember creating this topic with some tags:
This is my topic
It’s now displaying like this (note no tags):
Then later looking at this topic I noticed my tags on it - which don’t match the topic
Which is displaying with my tags from the other topic
I removed the tags from that post – is rare that topics here need tags and then only at most one or maybe two tags that can be used on multiple topics without confusion. This topic is a good example of tagging, ironically..
But I too noticed a few other topics had the same combination of odd tags shown – I also removed that particular combo of tags from another topic not pictured above.
This is a legit bug @eviltrout.
I have users who will tag everything 
Currently there is no other place to get an idea of how the tagging system might work and weed out possible problems.
Yes it is fine to test, but let’s please refrain from tagging things with ultra generic concepts like “button” or “post” or using three synonyms 
I can’t see adding tagging to a community until tag merging / aliasing is added - a process that involves moderating once and no user conversations.
Basically something that turns my tagging for these example topics into a non-issue.
On our forum only the Admin can create Tags.
I think this is the safest way to ensure it doesn’t get out of control.
True, we have members that will select inappropriate and / or too many tags for their topics, but that isn’t as bad as it would be if they could create their own.
And partially supported by Discourse’s Tagging process too. You can set which TL level can create tags, just set it to TL 4 (IIRC).
I would agree to @codinghorror, I wonder why would people add tags when the category name itself is self-describing. Multiple Tags never helped any way in SEO either, they are just for better user navigation and only when you use at most 1 or 2 tags. More than that makes no sense
Tagging should be TL2 and above here. At the bare minimum.