For this loop, and the loop below - it's more common to use a for loop.

for (Node *node = list.first, *node_next; node; node = node_next) {
  node_next = node->next;

  /* Code */
}

This has the advantage the looping logic is centralized in one place and you can use continue without causing problems.

Or you could use LISTBASE_FOREACH_MUTABLE.

Using the safe version of this function causes a list search.

Since this is looping on the seqbase there is no need to do this.

The purpose of this return value isn't clear, since this is the success of the last call to BLI_remlink_safe.

Should this be "all succeeded" "any succeeded" ?

This does remove sequences by calling BKE_sequencer_remove_flagged_sequences.

Where the function is named as if it's only tagging.

This changes behavior of remove, making it context dependent, which I'd rather avoid in scripting.

Also, we should support writing scripts that don't cause an excessive amount of searching.

Instead, we could have meta-strip remove method.