As they deliberately avoid sending spam tweets blocking them 'for' posting spam is not quite right and Twitter's options for reporting them correctly are therefore a bit limited.
The accounts are almost always female (according to their avatar) with digits at the end of their name, eg Jodie123. Their bios look similarly cut and paste with liberal use of dividers like ✦, ✶ or ✪ (I have to admit I use | and / in my bio, or did until I recently changed it).
- TV addict ✦ Professional Speaker ✦ Soccer fanatic ✦ Subtly charming geek ✦ 53 Countries since 2012
- Social media fan ✶ Author of fantasy books ✶ Travel consultant ✶ Beauty appreciator ✶ Technology lover
- Advocate for human dignity ✪ Spirituality ninja ✪ Sunglass fan ✪ Detoxification ✪ Nerd
In other words you can only really see the spam if you're in a position to be able to see the spam!
An example would be that you've tweeted about #homeopathy and a lot of similar-looking accounts retweet it. I suppose it's a tiny bit like #EverydaySexism which is largely invisible unless you're a woman who regularly experiences a range of men making comments at you. Different people moving through an otherwise identical space see and experience it very differently.
I am reporting these accounts as spam though I've not seen many of them being removed (I suspect Twitter just disagrees with my assessment because each account doesn't, individually, look particularly spammy). I'm not sure if Twitter pays attention to my pattern of reporting (ie several similar accounts in a short space of time) but I wish they did because then I think they'd notice the problem.
Perhaps Twitter isn't particularly bothered about these types of accounts. They aren't very harmful, beyond spouting nonsense into the Twittersphere (but let's face it we all do that too), they're not abusive and they're not posting the same tweeted link over and over again. But they don't contribute to the ecosphere.
While we're at it I still hate all those Sumall and Commun.it tweets that thank a bunch of strangers for tweeting (and do it in such a way that the tweet is visible to ALL of the tweeter's followers, and not just the strangers they're thanking - ugh).
What a depressing thought that future internet archaeologists will be left with the "(insight by commun.it)" tweets which, by volume alone, must surely be taking up plenty of Twitter's server space. Have a scroll though some of them and despair ;) Drivel.