This feedback was given multiple times, that somehow notifications in top panel doesn't blend very well..

From e.g Distrowatch review:

Two aspects of the Plasma interface I feel deserve more attention. The notification and settings area is especially well organized, I think. Pulling down the status bar shows us a grid of settings modules and we can tap one to bring up configuration options for items such as our wi-fi network, location, power saving and volume control. I think the settings are clearly labelled and well organized. The notifications I found to be a bit jumbled together. The notices were printed with small text and I found they were too close together.