I am probably guilty of this. In cases that require a little bit more investigation on my or a mod's part I always include a longer message, such as providing links and signposting to the relevant parts in cases of plagiarism, or explaining why I think a thread has run its course and deserves to be locked. However, the majority of my reports are for simple low/zero value meaningless shitposts which add nothing meaningful to the discussion, and I always report them with the same message, unless I think it's not complete obvious why it's spam (for example, if the post isn't bad, but is a rehash of something that has been said 10+ times already). I have a very low percentage of "bad" reports, so I had always assumed using the same message was acceptable.
Where is the balance to be had here? I could expand my report message for these kind of posts, but it would then take me probably around 10x longer to make a report, so 10x less posts being reported. Is the same repeated message fine in these cases of obvious spam?
It is acceptable, but you definitely run the risk of it being bad. Generally, spam posts are easy to figure out, and reporting them for "spam", "low quality content" or any other variation is usually fine, and perfectly acceptable. However, some posts which are being reported for being repeated or duplicate content, and not providing a reference runs a higher risk of being marked bad. When I receive a report like that I'll normally check the thread to a certain point, but I'm not going to go through a 200 page long thread for example looking for duplicate content. I'll use various plagiarism tools to see if that pings anything back, but if it doesn't then it'll be marked bad. The best practice when considering duplicate content or replies which have already been rehashed a few times is to include a reference. A lot of the time its obvious, and can be verified only a few replies up, and then its not a big deal. However, I've received messages from users who have reported something, and not included a reference, and the duplicate was over 20 pages ago.
Generally, use your common sense, and include detail in your report if its not obvious. I haven't noticed your reports honestly, and if you haven't received much bad reports I think its safe to say you're fine. We all fall guilty of it too I definitely did back in my reporting days, and I had a few marked bad where I didn't provide enough context, and then I reported it again with context, and it got deleted. Generally, I'm aware of threads which have a lot of spam in them, and it needs cleaning up. I've been busy recently, but I'll be visiting these threads periodically, and cleaning them up now that my activity should be back to normal.
In terms of my feature suggestion. I wouldn't mark down reports for specifying "spam", because that's all that's needed. That isn't a bad quality report. I'm not expecting essays or to nail everything, but sometimes a reference is absolutely appreciated. If you know that their reply is just rehashing what someone else said you've likely seen the original message, and providing that reference goes a long way, because the moderator handling the report hasn't seen it, and needs to go looking for it. This is my personal opinion obviously, and I'm not speaking on behalf of every other staff member, and I think the report quality suggestion definitely has bigger drawbacks than positives, but that's the only way I see running a competition/reward campaign like this to work.