...I've personally found new gems in threads such as "which altcoin is the best buy right now", so I'm probably more lenient than most towards these large, generic threads. I've also posted there myself. Their posts seemed "personal" to me, not a generic bot attempting to gain more posts.
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If you have the time/patience to sort through all the chaff to find people actually having a discussion in those spam megathreads then I can't argue with giving those people merit.
My primary concern is that one mindless shitposter spamming for bounty can churn out dozens of posts per day, and if enough of them are "accidentally" merited the whole spam problem starts up again.
Although suchmoon makes a good point that a jr. member with high activity/post count and just 1 or 2 merits will, indeed, stick out like a sore thumb now. Much more so than when there were a near-infinite number of newbies AND jr. members with 0 merit.