For larger projects this reload takes a long time (~20-30 seconds of unresponsiveness). The bug is easily noticeable when using Visual Studio on Windows, as the blue bar at the bottom will tell you that the project is reloading.

To reproduce with attached project:
1) Click Assets > Open C# Project to launch visual studio
2) Open 'SampleScene.unity' and enter playmode
3) Double click on error message in the console
4) Observe Visual Studio will Reload the Project
5) Exit Playmode + Enter Playmode
6) Click on error again
7) Notice Visual Studio will reload the project again DESPITE no code changes?

It appears that since ~2018.1.0b8 visual studio stopped giving the user the option to ignore a project reload, but would still want to do it. The project reload regression appears to have been initially introduced in 2018.1.0a5 - although here the reload will only occur after a number of attempts (can be over 5 repetitions of entering playmode / clicking on the error). From that version up the problem appears to have become progressively worse.

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From the User:

VCProjects loaded from the Unity Package Manager are detected in Visual Studio 2017 are too frequenlty being marked for reloading. This process takes up to a few minutes and really impedes workflow because during this process Visual Studio is locked up. This has been happening on Unity 2018.1.0b11, 2018.1.0b12, 2018.1.0b13, and the special version 2018.1.0b12 for ECS testing.