txgraph: drop NEEDS_SPLIT_ACCEPTABLE (simplification)

diff --git a/src/txgraph.cpp b/src/txgraph.cpp
index 274b14a4..492e13c8 100644
--- a/src/txgraph.cpp
+++ b/src/txgraph.cpp
@@ -42,8 +42,6 @@ enum class QualityLevel
     OVERSIZED_SINGLETON,
     /** This cluster may have multiple disconnected components, which are all NEEDS_RELINEARIZE. */
     NEEDS_SPLIT,
-    /** This cluster may have multiple disconnected components, which are all ACCEPTABLE. */
-    NEEDS_SPLIT_ACCEPTABLE,
     /** This cluster has undergone changes that warrant re-linearization. */
     NEEDS_RELINEARIZE,
     /** The minimal level of linearization has been performed, but it is not known to be optimal. */
@@ -128,10 +126,9 @@ public:
     // Generic helper functions.
 
     /** Whether the linearization of this Cluster can be exposed. */
-    bool IsAcceptable(bool after_split = false) const noexcept
+    bool IsAcceptable() const noexcept
     {
-        return m_quality == QualityLevel::ACCEPTABLE || m_quality == QualityLevel::OPTIMAL ||
-               (after_split && m_quality == QualityLevel::NEEDS_SPLIT_ACCEPTABLE);
+        return m_quality == QualityLevel::ACCEPTABLE || m_quality == QualityLevel::OPTIMAL;
     }
     /** Whether the linearization of this Cluster is optimal. */
     bool IsOptimal() const noexcept
@@ -145,8 +142,7 @@ public:
     /** Whether this cluster requires splitting. */
     bool NeedsSplitting() const noexcept
     {
-        return m_quality == QualityLevel::NEEDS_SPLIT ||
-               m_quality == QualityLevel::NEEDS_SPLIT_ACCEPTABLE;
+        return m_quality == QualityLevel::NEEDS_SPLIT;
     }
 
     /** Get the smallest number of transactions this Cluster is intended for. */
@@ -1179,37 +1175,20 @@ void GenericClusterImpl::ApplyRemovals(TxGraphImpl& graph, int level, std::span<
         to_remove = to_remove.subspan(1);
     } while(!to_remove.empty());
 
-    auto quality = m_quality;
     Assume(todo.Any());
     // Wipe from the Cluster's DepGraph (this is O(n) regardless of the number of entries
     // removed, so we benefit from batching all the removals).
     m_depgraph.RemoveTransactions(todo);
     m_mapping.resize(m_depgraph.PositionRange());
 
-    // First remove all removals at the end of the linearization.
-    while (!m_linearization.empty() && todo[m_linearization.back()]) {
-        todo.Reset(m_linearization.back());
-        m_linearization.pop_back();
-    }
-    if (todo.None()) {
-        // If no further removals remain, and thus all removals were at the end, we may be able
-        // to leave the cluster at a better quality level.
-        if (IsAcceptable(/*after_split=*/true)) {
-            quality = QualityLevel::NEEDS_SPLIT_ACCEPTABLE;
-        } else {
-            quality = QualityLevel::NEEDS_SPLIT;
-        }
-    } else {
-        // If more removals remain, filter those out of m_linearization.
-        m_linearization.erase(std::remove_if(
-            m_linearization.begin(),
-            m_linearization.end(),
-            [&](auto pos) { return todo[pos]; }), m_linearization.end());
-        quality = QualityLevel::NEEDS_SPLIT;
-    }
+    // Filter removed transactions out of m_linearization.
+    m_linearization.erase(std::remove_if(m_linearization.begin(), m_linearization.end(),
+                                         [&](auto pos) { return todo[pos]; }),
+                          m_linearization.end());
+
     Compact();
     graph.GetClusterSet(level).m_cluster_usage += TotalMemoryUsage();
-    graph.SetClusterQuality(level, m_quality, m_setindex, quality);
+    graph.SetClusterQuality(level, m_quality, m_setindex, QualityLevel::NEEDS_SPLIT);
     Updated(graph, level);
 }
 
@@ -1354,17 +1333,7 @@ bool GenericClusterImpl::Split(TxGraphImpl& graph, int level) noexcept
     // This function can only be called when the Cluster needs splitting.
     Assume(NeedsSplitting());
     // Determine the new quality the split-off Clusters will have.
-    QualityLevel new_quality = IsAcceptable(/*after_split=*/true) ? QualityLevel::ACCEPTABLE
-                                                                  : QualityLevel::NEEDS_RELINEARIZE;
-    // If we're going to produce ACCEPTABLE clusters (i.e., when in NEEDS_SPLIT_ACCEPTABLE), we
-    // need to post-linearize to make sure the split-out versions are all connected (as
-    // connectivity may have changed by removing part of the cluster). This could be done on each
-    // resulting split-out cluster separately, but it is simpler to do it once up front before
-    // splitting. This step is not necessary if the resulting clusters are NEEDS_RELINEARIZE, as
-    // they will be post-linearized anyway in MakeAcceptable().
-    if (new_quality == QualityLevel::ACCEPTABLE) {
-        PostLinearize(m_depgraph, m_linearization);
-    }
+    QualityLevel new_quality = QualityLevel::NEEDS_RELINEARIZE;
     /** Which positions are still left in this Cluster. */
     auto todo = m_depgraph.Positions();
     /** Mapping from transaction positions in this Cluster to the Cluster where it ends up, and
@@ -1771,11 +1740,9 @@ void TxGraphImpl::SplitAll(int up_to_level) noexcept
     // Before splitting all Cluster, first make sure all removals are applied.
     ApplyRemovals(up_to_level);
     for (int level = 0; level <= up_to_level; ++level) {
-        for (auto quality : {QualityLevel::NEEDS_SPLIT, QualityLevel::NEEDS_SPLIT_ACCEPTABLE}) {
-            auto& queue = GetClusterSet(level).m_clusters[int(quality)];
-            while (!queue.empty()) {
-                Split(*queue.back().get(), level);
-            }
+        auto& queue = GetClusterSet(level).m_clusters[int(QualityLevel::NEEDS_SPLIT)];
+        while (!queue.empty()) {
+            Split(*queue.back().get(), level);
         }
     }
 }
@@ -2640,10 +2607,8 @@ void GenericClusterImpl::SetFee(TxGraphImpl& graph, int level, DepGraphIndex idx
     m_depgraph.FeeRate(idx).fee = fee;
     if (m_quality == QualityLevel::OVERSIZED_SINGLETON) {
         // Nothing to do.
-    } else if (!NeedsSplitting()) {
+    } else if (IsAcceptable()) {
         graph.SetClusterQuality(level, m_quality, m_setindex, QualityLevel::NEEDS_RELINEARIZE);
-    } else {
-        graph.SetClusterQuality(level, m_quality, m_setindex, QualityLevel::NEEDS_SPLIT);
     }
     Updated(graph, level);
 }