As a long time SEO professional I see this system very much similar to PageRank, and it will have a number of benefits and pitfalls of the PageRank system.

The benefits are obvious and great, it will reduce spamming by requiring additional tasks.

Now going to the potential pitfalls -
1) Merit farming on paid sites. Some members have suggested banning/penalizing members purchasing this. The problem here however is the same as negative SEO - how do you prove someone bought it? And if people receive merit from a "paid source" and get banned for it, you could then buy paid merit for people you don't like to get them banned or penalized.

2) Reciprocal merit telegram groups. To make it less obvious there could be "merit chains" of 3 people or more.

3) Alt-chain merit giving. Once 10 alt accounts or so have enough merit, they could now use their monthly allowance to instantly pass the merit requirements on their new alt accounts. This would make identifying alts easier of course and is easily solvable by a rule that would disallow this. But since alt accounts are allowed according to the forum rules, it waits to be seen what the admins point of view will be regarding this.

Point 1) and 3) are easily solved by retroactively removing merit given from an identified corrupt merit-giving account, and also removing all sMerit capability from the corrupt account (+other penalty maybe?).

Point 2) will be very, very difficult to combat.

The overall problem here is that professional spammers will utilize their network of spammers and finances to circumvent the merit system, whereas non-professional spammers will be stopped in their tracks. This is kind of like a central power monopolizing corruption to only the most professional corrupt bodies (kind of like the extensive licensing needed for a bank or casino where only the best malicious actors can thrive: ie highly organized crime syndicates, or corruptly-networked individuals that can crash the financial system with crappy equity-baskets with AAA ratings).

At the end of the day it's very unlikely any automated system can overcome the spam. However as an overall I think the merit system is nevertheless good since at least it adds an additional barrier to overcome for spammers. I like and prefer however where trusted community members can simply give red trust to obvious spammers, thus preventing them from meeting the requirements for signature campaigns. It will be good to see both of these systems acting as deterrence against spam together.

PS: Awarding default merit to all existing members is a problem I think. There's already tonnes of farmed hero/legendary accounts that will have huge amounts of monthly sMerit.. permanently. My idea: Make this "free" initial merit expire after 1 year. That gives all members 1 year to make enough quality posts to retain their ranking.