I should have thought of that earlier.

Those aren't indexes. They're automatically created column statistics. The query optimiser creates those to better know the data distribution within a column.

You can drop them. SQL will recreate them if necessary.

For each of the entries in sysindexes that begin with _WA_Sys, run the following

DROP STATISTICS auto.<Statistic Name>

Statistics can indicate a column where an index would be useful, so you may want to watch which columns get stats and consider creating indexes on them. Also, from what I saw of the column names, your table is highly unnormalised. Is that intentional?