Merge bitcoin#24305: Docs: [policy] Remove outdated confusing comment

e50a9be Remove outdated comment on CFeeRate (Murch)

Pull request description:

  This comment described how the constructor of CFeeRate was previously indirectly used to parse fee rate arguments from RPCs. The command line input was actually in sat/vB but due to the use of AmountFromValue() it got converted to BTC/vB which then got rectified in the constructor by creating a CFeeRate from that given value and COIN as the transaction size. Since this usage pattern was removed from the codebase some months ago, the comment is now obsolete.

ACKs for top commit:
  michaelfolkson:
    ACK e50a9be
  jonatack:
    ACK e50a9be

Tree-SHA512: f17bf0baeeca85a5c7883edadd407da845f6e3af1c949e93116bd67c02e601682a5f7f1ab2497172472e3acf1c4e3c234b01161a77e7d7f028e3551da34777f0

src/policy/feerate.h

@@ -24,34 +24,38 @@ enum class FeeEstimateMode {
 };
 
 /**
- * Fee rate in satoshis per kilobyte: CAmount / kB
+ * Fee rate in satoshis per kilovirtualbyte: CAmount / kvB
  */
 class CFeeRate
 {
 private:
-    CAmount nSatoshisPerK; // unit is satoshis-per-1,000-bytes
+    /** Fee rate in sat/kvB (satoshis per 1000 virtualbytes) */
+    CAmount nSatoshisPerK;
 
 public:
-    /** Fee rate of 0 satoshis per kB */
+    /** Fee rate of 0 satoshis per kvB */
     CFeeRate() : nSatoshisPerK(0) { }
     template<typename I>
     explicit CFeeRate(const I _nSatoshisPerK): nSatoshisPerK(_nSatoshisPerK) {
         // We've previously had bugs creep in from silent double->int conversion...
         static_assert(std::is_integral<I>::value, "CFeeRate should be used without floats");
     }
-    /** Constructor for a fee rate in satoshis per kB (duff/kB).
+
+    /**
+     * Construct a fee rate from a fee in satoshis and a vsize in vB.
      *
-     *  Passing a num_bytes value of COIN (1e8) returns a fee rate in satoshis per B (sat/B),
-     *  e.g. (nFeePaid * 1e8 / 1e3) == (nFeePaid / 1e5),
-     *  where 1e5 is the ratio to convert from DASH/kB to sat/B.
+     * param@[in]   nFeePaid    The fee paid by a transaction, in satoshis
+     * param@[in]   num_bytes   The vsize of a transaction, in vbytes.
      */
     CFeeRate(const CAmount& nFeePaid, uint32_t num_bytes);
+
     /**
-     * Return the fee in satoshis for the given size in bytes.
+     * Return the fee in satoshis for the given size in vbytes.
      */
     CAmount GetFee(uint32_t num_bytes) const;
+
     /**
-     * Return the fee in satoshis for a size of 1000 bytes
+     * Return the fee in satoshis for a vsize of 1000 vbytes
      */
     CAmount GetFeePerK() const { return nSatoshisPerK; }
     friend bool operator<(const CFeeRate& a, const CFeeRate& b) { return a.nSatoshisPerK < b.nSatoshisPerK; }