If a series of tweets can easily be put into a defined order for consumption then why not just lift the max character limitation and let people make tweets as long as they want? Seems like it’d be an easy slide down that slope once you’re on it.
There is no slope. Either the limitation is there, or it isn't. What comes after to call this a "slippery slope"?
And clearly the existing limitation is a pain in the ass, or else services that "unroll" multi-tweet text wouldn't exist. The limitation is completely arbitrary and clearly not entirely helpful, so a request to lift it is entirely reasonable.
Would that be an issue? The character limit is clearly a pain point for some users (graph here[1] of average tweet lengths -- many people abandon their tweets if they hit the limit), so why not alleviate it? Especially given that it doesn't appear to impact other users' behaviour: only 5% of users actually used the extra space during testing of the increase from 140 to 280 characters [2].
This discussion reminds me of when Instagram stopped enforcing that all pictures be square, a (mostly) ideological limit that made using the service harder.