Should tags be pluralised or singular?
It's pretty standard on the other sites I use to use the plural version of tags along with the -ing version of many nouns (on Arts and Crafts, we use "crocheting" instead of "crochet", for example). You can see this standard in the tags you've used on this question. Those tags are tags and tagging.
Other notes, tags should use the US English spelling structure. This is also standardized on MSE.
Does SOFU have an accepted standard on language and spelling? Which is it?
For bodies, no. For tags, US-English.
Titles don't actually need to be consistent (tags absolutely do!), but if you think anyone might want to search for a question then you would do well to use the more common spelling - whichever that might happen to be...
So, from a brief scan of existing tags, we should consider fixing:
- argument --> arguments
- party --> parties
- extrovert -->extroverts
- online-interaction --> online-interactions
For many of these, though, the system will not allow the plural tag to be created except by a moderator/CM, so we will need to request the CMs to make this change or wait until we have pro-tem mods.
All of this leaves a bit of room, though. We don't have to be draconian about it. It's about setting a standard and being thoughtful about what makes sense, particularly when some words can be used multiple ways.