Please explain your feature request to the best of your abilities:

Add a command (such as /t toggle plotresale) for towns to determine whether plots put themselves back for sale upon a resident leaving/purging.

Currently towns circumvent unwanted purchases of plots put back for sale by setting high plotprice (i.e /t set plotprice 10000). Having the ability to toggle plotresale would just result in plots being reclaimed by the town and nfs.

I do like the idea of making this a thing for mayors to decide but I thought I'd also make sure you're aware of a global setting that does this already:

"town.default_taxes.does_non-payment_place_plot_for_sale",
"false",
"",
"# Does a player's plot get put up for sale if they are unable to pay the plot tax?",
"# When false the plot becomes town land and must be set up for-sale by town mayor or staff."),

Would enabling this work with taxes disabled, and does it only apply to plots put up for sale after failing to pay plot tax (or general removal)?

Yeah this setting is only used when plots are lost due to non-payment of taxes. I wasn't thinking about when players leave/are purged.