A small script for Ian Lloyd. Pass text to it on stdin and it outputs that same text with spelling errors highlighted. Change the highlight characters at the top if you need to.

sil-aspell-highlighter.py

#!/usr/bin/env python3
import sys, subprocess
HIGHLIGHT_BEFORE = "👉"
HIGHLIGHT_AFTER = "👈" # if you just want a highlight before, make this ""
cmd = ["aspell", "pipe"]
# add any extra options given to our command to the aspell command
if len(sys.argv) > 2:
    cmd += sys.argv[1:]
for line in sys.stdin.readlines():
    # feed the line to aspell; will throw obvious error on failure
    proc = subprocess.run(cmd, input=line, text=True, capture_output=True)
    corrections = []
    for oline in proc.stdout.split("\n"):
        if not oline.startswith("&"): continue
        parts = oline.split()
        from_start = int(parts[3][:-1]) # will be 28: so strip off colon
        corrections.append((from_start, from_start + len(parts[1])))
    if not corrections: continue
    # Once we've got all the corrections, handle them in reverse order
    # so that the indices for later ones aren't affected by earlier
    new_line = line[:].strip()
    for start, end in sorted(corrections, key=lambda n:n[0], reverse=True):
        new_line = new_line[:end] + HIGHLIGHT_AFTER + new_line[end:]
        new_line = new_line[:start] + HIGHLIGHT_BEFORE + new_line[start:]
    print(new_line)

So it should be possible to run this as python3 sil-aspell-highlighter.py anywhere where you might have run aspell.

Pass additional args to this script to pass them to aspell. So if you need a list of words to ignore, create a file which is in $HOME/some/folder/mydict.en.pws, make the first line be personal_ws-1.1 en 0, put one ignored word per line, and then run this as

python3 sil-aspell-highlighter.py --personal=mydict.en.pws --home-dir=$HOME/some/folder/