The only issue with text only files that I have ever seen is that you have to WRITE more descriptively since now you have eliminated the use of images when explaining item.
Thus, it takes longer to write and you have to ALWAYS assume the person reading it has the bare minimum basde knowledge of whatever needs fixing and the step by step has to be VERY precise.
You become a very highly paid technical writer of a very complex solution.
I document using MS Word (or VISIO is some cases) convert to PDF and then post. I always page number (page x of y) and auto-date the doc so that we always know at a glance if that if two are seen we can tell what is the latest version. Putting in the page x of y also lets a person know how long the instruction set is so they have the expectation / time factor knowledge which makes them work better. Like the . . . . . . ant trail when installing so you know how long it is going to take.