As I understand your argument:
"We don't offer formatting because IE users don't understand HTML".
(Is that your intention?)
- As argued in a comment, I doubt the correlation you assume
- Even if such a correlation would exist, it is not static.
- You mix up feature and implementation:
The feature you (want to) remove is rich text formatting. By following the stereotype in your question, IE users are more likely to expect that. because they know, you know, Word: "Where's the "[B]" button?"
The implementation you chose is apparently to represent them as HTML tags. Now, that is going to confuse my mom: "Clicking the [B] button doesn't work." (Yes, that's what my mom says. If I'm lucky, she tells me something about "funny symbols".)
Your general question is interesting, though.
(1) The most common approach is:
- Market determines features and audiences
- Features and audiences determine UX
i.e. the UX has to deliver whatever it's asked for, dropping the feature because of complex UX can happen, but is a secondary.
Features roughly get sorted by
additional revenue / implementation cost (I use the terms losely here, revenue could be Stallman Karma for OSS projects), and are dropped below a given threshold.
An additional feature can drive up cost, and reduce users (because they stop liking it).
(This formula is to simple to drive a decision, of course, since features are interconnected, e.g. supporting different platforms can affect the cost of many other features.)
Your question comes in after this: when you can't build your UX to remain simple after the addition of the new features, or the cost of that would become to high, you rather drop that feature.
(2) OTOH, there's a good market for "the most simple tool to do X":
- start with the required user interface
- see what features you can cover with that without extending the UI
That's very similar to the case above, only you assume a sharply declinig user base when the UX gets more complex.
(In any case it's a good approach to avoid having to cut features.)