In every airplane I know of (except the Stearman and the F-16), the horizontal stabilizer provides down-force to hold the nose up, as the c.g. is forward of the center of lift.

Normally this force is only about 5% or so of the total lift provided by the wings. If the wings are lifting an airplane that weighs 100,000 lbs, the wings must lift 105,000 lbs, and the tail "pushes down" 5,000 lbs. Net result: steady-state flight (no nose movement up or down).

When flaps are extended, there is a significant downwash change. In other words, the air no longer streams straight back from the wing---it is "deflected" downward. As this downwash increasingly impacts the top-surface of the Horizontal, it would normally tend to increase the down-force--which would normally make you pitch-up.

However, this may be offset by the nose-down moment caused by extending flaps. In every airplane I've flown, a significant amount of nose-up trim (ie, increased tail down-force) is required as the flaps are extended.

In a T-tail design, the increased downwash--which normally somewhat compensates for the nose-down moment of extending flaps--is removed, because the horizontal is high enough it is not affected by the downwash. This means you must compensate by pulling back on the stick, or trimming the entire Horizontal (on aircraft so equipped, such as jets).

If only pulling-back on the stick, you may achieve a point where the elevator cannot provide sufficient force to overcome the nose-down pitching moment of the flaps, OR, the elevator itself may stall.

In the Lear family (20s and 30s), even with a trimmable Horizontal, there may not be enough force available, and if heavy ice was confirmed, or tail ice suspected, you were supposed to land flaps-up or minimal flap.

And the Lear 35 has heated emmpenage.

As to why the tail may or may not develop more ice: I've never heard the pointy-er, the more ice. I would have believed just the opposite. The boundary layer increases in depth from nose to tail of fuselage, or leading to trailing edge of surfaces.

Boundary-layer air is air that "isn't moving as fast as the free-stream." For air to slow down, it usually expands, then slows. When air expands, it cools off, and increases the likelhood any remaining mosture will be deposited as ice.

Last idea on the topic: perhaps the CRJ, with swept wings, benefits from spanwise flow. That is, "downwash" in the horizontal sense. Except in supersonic flow, air going over a swept-wing "bends" and tries to flow slightly outboard. This spanwise flow causes AOA to be "apparently" higher at the wingtips, and will cause tip-stall first, unless the wing has reflexive-twist or aerodynamic washout.

So, if the flow is moving away from the fuselage due to wing-sweep, it may carry the bulk of the moisture-laden air that would cause ice with it.