My way of doing twitter but on hive,

• I would post all 'tweets' to comments of a post by the dapp account, A new post is made once a day. (for upvotes to help support the dapp and so the comments on one post don't get too messy)
• any replys would be children of said comments,
• Comments give lower rewards there for you can't complain about shortform getting huge rewards.
• I'd make a front end that would format these comments into 'tweets' and associated replys in a readable way.
• All replys and 'tweets' can be upvoted.
• No one would generally see the spam unless they specifically looked at the Dapps posts containing all the comments.

At the end of the day the idea is to store the 'tweet' on hive while having a frontend to properly display them as short form content.
Character limits would apply similar to twitter for cross posting potential.
I'd find a way so that any posts or comments made outside of our own front end would be filtered out if not following correct posting format etc.