The karma minimum is in place to keep spam bots and self-promotion bots from flooding users' feeds with posts that aren't necessarily linked to mindfulness.

• You haven't accumulated more than 125 karma. The bot's total karma does not include awarder, awardee, or link karma.
• To post, you'll need 125 karma, and to remark, you'll need 75 karma.
• Create one if you don't already have one — it's free and simple. Locate and click the Create Your Own Subreddit button on the homepage's right-hand sidebar.
• To create a subreddit, you'll need roughly 50 (not precisely, but close) combined karma.

Read More: What's Reddit Gold and why do people “give” Reddit Gold?