The fear is real, most of the time you forget, leave it on and then you have a total destruction of parts and it’s too late, you never noticed and your mesh is ruined.
For the vertex being part of the edge, you do have to subdivide the edge first in order to get a vertex there, then span vertex with vertex and then M to merge by distance. You need that vertex there because an edge always needs to have a vertex at each end and by their vertices is how they fuse together.
