I’ve switched between HTC, Samsung, and Nexus phones a lot over the years. I noticed some junk data in my contacts a long time ago, but I didn’t get annoyed enough to fix it until this weekend.
The issue is that HTC leaves a lot of metadata behind it in your contacts. If you’re affected by this you’ll see a lot of this kind of malarkey:
I wrote a small Android app to clear this up. If you synchronise your Google contacts then the fix will propagate to them too. You can have a look at the source code or download a debug APK from GitHub.