When minecarts are shot with a bow, the dropped item will be named "entity.minecartRideable.name", appearing in italic as with a custom name from an anvil. This occurs on Realms, so it is not a plugin bug. OptiFine is installed, but this shouldn't affect it. I have included the output log for going on to my Realm, placing a minecart, shooting it in survival, and then quitting.
MC-104521
Minecart Tooltip Bug
Resolved
Invalid
0
Thank you for your report.
However, your ticket has been resolved as invalid.
This ticket relates to a modified or 3rd party client, server, or launcher.
Any non-standard client/server/launcher build needs to be taken up with the appropriate team, not Mojang.
Any plugin issues need to be addressed to the creator of the plugin or resource pack.
This site is for addressing issues related to the base unmodded Minecraft; Bukkit/Spigot, Forge, Optifine, modded servers such as The Hive, Overcast, Showbot, Hypixel or any other modded system invalidates your ticket, unless the behavior can be reproduced in Vanilla.
Additionally, if you have problems on large-scale modded servers, please report it to their site. It's probably not a bug in Vanilla Minecraft.
:info: If you are able to reproduce your issue in a vanilla environment, feel free to create a new ticket.