This would be the better solution, indeed. You'll likely need to query the core [[https://www.mediawiki.org/wiki/Manual:logging_table|logging table]] to get the name of the user who deleted a comment, though.

I was thinking of just clearing comment text without printing the user's (owner) name similar to the sample provided by @SamanthaNguyen. Is it a good idea?

I am able to reproduce this bug. I would like to propose two solutions to this:

1. If parent comment is deleted, then delete the entire thread. This doesn't sound right to me, because if there are 100 replies then the entire conversation is gone, which is not a good idea as there may be something useful in there for future reference.
2. If parent comment is deleted, then display some text like "This comment was deleted by owner" and keep all the replies as it is. Moreover, an admin may have rights to delete the entire thread.

I am new to WikiMedia and I would like to work on this. Could someone provide more pointers on how should I start?
Note that I already have the core and extension/Comments repository cloned from Gerrit.