Find and replace comma separated values

Jeffrey T 

You can try using the Fuzzy matching option in the Merge Queries function in Power Query.

I created two queries for your tables - data and lookup (respectively).

Then this:

let
    Source = data,

    split 
        = Table.ExpandListColumn(
            Table.TransformColumns(
                Source,
                {{"company", Splitter.SplitTextByDelimiter(", ")}}),
            "company"
        ),

    fuzzy 
        = Table.FuzzyNestedJoin(
            split,{"company"}, 
            lookup, {"CompanyName"}, 
            "lookup",
            JoinKind.LeftOuter, 
            [IgnoreCase=true, IgnoreSpace=true, NumberOfMatches=1, Threshold=0.5]
        ),

    expand 
        = Table.ExpandTableColumn(
            fuzzy,
            "lookup",
            {"CompanyCode", "CompanyName"},
            {"CompanyCode", "CompanyName"}
        ),

    mergedcompany 
        = Table.AddColumn(
            expand,
            "mergedCompanyName",
            each if [CompanyName] = null then [company] else [CompanyName]
        ),

    group 
        = Table.Group(
            mergedcompany,
            {"username"},
            {
                {"Original", each Text.Combine([company],", ")},
                {"Replaced", each Text.Combine([mergedCompanyName],", ")}
            }
        )
in
    group

This is what the result looks like: