"Why didn't this product get marked down at all?"
Most often, a missing or invalid end date. Markdown pricing plans toward a deadline, so without a usable end date it can't build a schedule and leaves the price as-is, and it's flagged in the run's errors. Check the product's end date or the campaign's end date. See How Markdown & Clearance Pricing Works.
"Why did clearance drop the price below cost?"
That's clearance working as designed. As the deadline nears and stock isn't moving, the price floor is gradually lowered to allow a controlled loss, because unsold stock at the deadline is worth even less. If selling below cost isn't acceptable, use Max Profit or Max Revenue with a firm margin floor instead of Clearance. See Choosing a Markdown Objective.
"I set Max Profit but the suggestions look like Max Revenue. Why?"
If any product in the run is missing cost data, profit can't be calculated, so the whole run falls back to Max Revenue (and says so in its notices). Supply complete cost data to keep it on Max Profit. See Choosing a Markdown Objective.
"Why won't it discount this product any further?"
Probably because it would already sell out at the current discount. The system caps its forecast at your stock on hand, so cutting deeper wouldn't sell more units; it would just give away margin. See How Markdown & Clearance Pricing Works.
"Why is one slow product being marked down faster than the others?"
The pace follows whichever is more urgent: the calendar or the actual stock depletion. A product that isn't selling, with stock still on hand and the deadline approaching, gets marked down faster to catch up, while a brisk seller rides the gentler calendar pace. See the "two clocks" section of How Markdown & Clearance Pricing Works.
"How is this different from regular price optimization?"
Regular optimization finds the best ongoing price with no deadline and no regard for stock levels. Markdown pricing plans a path of prices over a fixed window to sell through a known quantity by a date, and it treats leftover stock as a cost. Use markdown when there's a deadline and inventory to clear; use everyday optimization otherwise. See Dynamic Pricing vs. Price Optimization.