>> because text properties on strings can't be saved
>> in the desktop file or by other history saving libraries.
>
> Couldn't we change that instead?

It seems text properties is the least bad of all other alternatives
that are not backward compatible and don't allow adding support for
search parameters to query-replace such as requested in bug#22479,
so with text properties this seems to be a better way, and adding
support to desktop for text properties is not unachievable: