Start with empty preferences: various preferences are marked as modified

[simon04]

What steps will reproduce the problem?

Start JOSM with empty preferences

java -Djosm.home=/tmp/.josm -jar dist/josm-custom.jar 
2020-01-30 10:45:34.772 INFO: Log level is at INFO (INFO, 800)
2020-01-30 10:45:34.808 INFO: Missing preference file '/tmp/.josm/preferences.xml'. Creating a default preference file.

What is the expected result?

What happens instead?

The following preferences are marked as modified (the ones marked as diff deleted are unexpected):

 cache.capabilities1637351842
 cache.motd.html
 cache.motd.html.java
 cache.motd.html.lang
 cache.motd.html.version
-draw.rawgps.lines
 expert
-imagery.entries
-imagery.layers.default
 josm.version
-mappaint.renderer-class-name
-mappaint.style.known-defaults
 mirror.https://josm.openstreetmap.de/maps
 mirror.https://query.wikidata.org/sparql?query_SELECT+%3FOSM_key+%3Fformatter_URL+WHERE+%7B%0A++%7B+%3Fitem+wdt%3AP1282+%3FOSM_key.+%7D%0A++FILTER%28STRSTARTS%28%3FOSM_key%2C+%27Key%3A%27%29%29+.%0A%0A++%7B%0A++++%7B+%3Fitem+wdt%3AP1630+%3Fformatter_URL.+%7D%0A++++UNION%0A++++%7B+%3Fitem+wdt%3AP3303+%3Fformatter_URL.+%7D%0A++%7D%0A%7D%0A
mirror.https://sophox.org/sparql?query_SELECT+%28CONCAT%28%22Key%3A%22%2C+%3Fpermanent_key_ID%29+as+%3FOSM_key%29+%3Fformatter_URL+WHERE+%7B%0A++%3Fitem+osmdt%3AP2+osmd%3AQ7.%0A++%3Fitem+osmdt%3AP16+%3Fpermanent_key_ID.%0A++%3Fitem+osmdt%3AP8+%3Fformatter_URL.%0A%7D%0A
-preferences.reset.draw.rawgps.lines

Please provide any additional information below. Attach a screenshot if possible.

Revision:15793
Is-Local-Build:true
Build-Date:2020-01-30 10:45:24

Identification: JOSM/1.5 (15793 SVN en_GB) Linux Arch Linux
Memory Usage: 502 MB / 3976 MB (297 MB allocated, but free)
Java version: 11.0.6+10, Oracle Corporation, OpenJDK 64-Bit Server VM
Screen: :0.0 2560x1440
Maximum Screen Size: 2560x1440
VM arguments: [-Djosm.home=<josm.pref>]

Last errors/warnings:
- W: No configuration settings found.  Using hardcoded default values for all pools.
- W: Region [TMS_BLOCK_v2] Resetting cache
- W: Region [WMS_BLOCK_v2] Resetting cache
- W: Region [WMTS_BLOCK_v2] Resetting cache