There is less spam on the blockchain these days. However, I don't think we have the Hardfork to thank for that. Instead, I think the level of spam in the blockchain has decreased more because of the low price of STEEM.
Why not the Hardfork?
If we consider the Resource Credit (RC) System, unless you are a very new account with no RC to your name, you really won't be affected by the limits it has imposed. My account, for example, with its 395 Steem Power has enough RCs to make more than 100 comments with no real impact to the account. In fact, according to Steemd.com, with each comment or post using up about 0.9RC and with my account regenerating about 80million RCs per day, my account's daily RC recharge alone is enough to cover 80 comments every day.
If I were a spammer, which I'm not, I will have more than enough RCs to spam to my heart's content. Granted, there are accounts with less RCs than mine, but even at a quarter of my current SP, that's still enough for 20 spammy comments everyday. So, really the only accounts affected by the RC limits are the new ones.
But, what to do I think is the reason for the reduced amount of spam in the blockchain?
Here's the thing, it's less profitable to post in the blockchain right now that the price of STEEM is just worth $0.28 than it was a year ago when STEEM was hovering between $6 and $8 or even six months ago when STEEM was within the $2 level. That means that spammers will be earning less for their efforts because of the low price of STEEM. Thus, it's not worth it to post spammy comments or posts because they will just be getting pennies for their efforts. To be honest, this is one of the silver linings to the low price of STEEM--most of the users active on the blockchain are those who are here for the content whether as producers or consumers of it.
That's why I'm guessing you can expect the amount of spam to increase again once the STEEM price recovers and spamming becomes profitable again. Sadly, that's the nature of the Internet--opportunists like spammers tend to flock to platforms that are profitable. And because STEEM is not profitable at the moment, they're probably off spending their time elsewhere.
TL;DR: I don't think the Hardfork had much to do with the decrease of spam in the blockchain. Instead, it's the low price of STEEM, which has made the platform (and as a consequence spamming) less profitable and has driven most spammers away...for now.
Hope this helps.
LESS. Because posting requires RC now, people will use their RC more carefully.
The situation is way better after HardFork 20. I don't see as much spam nowadays, or I'm just lucky spammers are avoiding me.
I thing the Resource Credit system has changed the game, spammers with low SP are not able to post and comment as much as they did before and since they are not capable of posting and earning, there's less possibility for spamming.